GeoTIFF Format Specification
GeoTIFF Revision 1.0
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   Specification Version: 1.8.1 
   Last Modified: 31 October, 1995

Authors:

   Niles Ritter, Jet Propulsion Laboratory
   Cartographic Applications Group
   4800 Oak Grove Dr.
   Pasadena, CA 91109
   email:ndr@tazboy.jpl.nasa.gov      
   
   Mike Ruth, SPOT Image Corp
   Product Development Group
   1897 Preston White Dr.
   Reston, VA 22091
   email:ruth@spot.com

Acknowledgments:

GeoTIFF Working Group:
    Mike Ruth, Niles Ritter, Ed Grissom, Brett Borup, George Galang,
    John Haller, Gary Stephenson, Steve Covington, Tim Nagy, 
    Jamie Moyers, Jim Stickley,Joe Messina, Yves Somer.

Additional advice from discussions with Tom Lane, Sam Leffler regarding      
TIFF implementations. 

Roger Lott, Fredrik Lundh, and Jarle Land provided valuable information    
regarding projections, projection code databases and geodetics.
   
GeoTIFF Mailing list:  
    Posting: geotiff@tazboy.jpl.nasa.gov
    Subscription: geotiff-request@tazboy.jpl.nasa.gov
       (send message "subscribe geotiff your-name-here").
   
Disclaimers and Notes for This Version:

This proposal has not been approved by SPOT, JPL, or any other organization. This represents a proposal, which derives from many discussions between an international body of TIFF users and developers.
 
The authors and their sponsors assume no liability for any special, incidental, indirect or consequences of any kind, or any damages whatsoever resulting from loss of use, data or profits, whether or not advised of the possibility of damage, and on any theory of liability, arising out of or in connection with the use of this specification.

Copyright

Portions of this specification are copyrighted by Niles Ritter and Mike Ruth. Permission to copy without fee all or part of this material is granted provided that the copies are not made or distributed for direct or commercial advantage and this copyright notice appears.
  
Licenses and Trademarks

Aldus and Adobe are registered trademarks, and TIFF is a registered trademark of Aldus Corp., now owned by Adobe. SPOT Image, ESRI, ERDAS, ARC/Info, Intergraph and Softdesk are registered trademarks. 
Concurrence

  The following members of the GeoTIFF working group have reviewed and approved of this revision. 
   
   Name                   Organization              Representing
   --------------------   -----------------------   ------------
   Niles Ritter           Jet Propulsion Labs       JPL Carto Group
   Mike Ruth              SPOT Image Corp. (USA)     SPOT Image Corp. (USA)
   
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Table of Contents
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1  Introduction  
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1.1 About this Specification

This is a description of a proposal to specify the content and structure of a group of industry-standard tag sets for the management of georeference or geocoded raster imagery using Aldus-Adobe's public domain Tagged-Image File Format (TIFF). 
  
This specification closely follows the organization and structure of the TIFF specification document.
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1.1.1 Background

TIFF has emerged as one of the world's most popular raster file formats. But TIFF remains limited in cartographic applications, since no publicly available, stable structure for conveying geographic information presently exists in the public domain.

Several private solutions exist for recording cartographic information in TIFF tags. Intergraph has a mature and sophisticated geotie tag implementation, but this remains within the private TIFF tagset registered exclusively to Intergraph. Other companies (such as ESRI, and Island Graphics) have geographic solutions which are also proprietary or limited by specific application to their software's architecture. 

Many GIS companies, raster data providers, and their clients have requested that the companies concerned with delivery and exploitation of raster geographic imagery develop a publicly available, platform interoperable standard for the support of geographic TIFF imagery. Such TIFF imagery would originate from satellite imaging platforms, aerial platforms, scans of aerial photography or paper maps, or as a result of geographic analysis. TIFF images which were supported by the public "geotie" tagset would be able to be read and positioned correctly in any GIS or digital mapping system which supports the "GeoTIFF" standard, as proposed in this document. 

The savings to the users and providers of raster data and exploitation softwares are potentially significant. With a platform interoperable GeoTIFF file, companies could stop spending excessive development resource in support of any and all proprietary formats which are invented. Data providers may be able to produce off-the-shelf imagery products which can be delivered in the "generic" TIFF format quickly and possibly at lower cost. End-users will have the advantage of developed software that exploits the GeoTIFF tags transparently. Most importantly, the same raster TIFF image which can be read and modified in one GIS environment may be equally exploitable in another GIS environment without requiring any file duplication or import/export operation. 
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1.1.2 History

The initial efforts to define a TIFF "geotie" specification began under the leadership of Ed Grissom at Intergraph, and others in the early 1990's. In 1994 a formal GeoTIFF mailing-list was created and maintained by Niles Ritter at JPL, which quickly grew to over 140 subscribers from government and industry. The purpose of the list is to discuss common goals and interests in developing an industry-wide GeoTIFF standard, and culminated in a conference in March of 1995 hosted by SPOT Image, with representatives from USGS, Intergraph, ESRI, ERDAS, SoftDesk, MapInfo, NASA/JPL, and others, in which the current working proposal for GeoTIFF was outlined. The outline was condensed into a prerelease GeoTIFF specification document by Niles Ritter, and Mike Ruth of SPOT Image.
Following discussions with Dr. Roger Lott of the European Petroleum Survey Group (EPSG), the GeoTIFF projection parametrization method was extensively modified, and brought into compatibility with both the POSC Epicentre model, and the Federal Geographic Data Committee (FGDC) metadata approaches.
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1.1.3 Scope

The GeoTIFF spec defines a set of TIFF tags provided to describe all "Cartographic" information associated with TIFF imagery that originates from satellite imaging systems, scanned aerial photography, scanned maps, digital elevation models, or as a result of geographic analyses. Its aim is to allow means for tying a raster image to a known model space or map projection, and for describing those projections.

GeoTIFF does not intend to become a replacement for existing geographic data interchange standards, such as the USGS SDTS standard or the FGDC metadata standard. Rather, it aims to augment an existing popular raster-data format to support georeferencing and geocoding information.

The tags documented in this spec are to be considered completely orthogonal to the raster-data descriptions of the TIFF spec, and impose no restrictions on how the standard TIFF tags are to be interpreted, which color spaces or compression types are to be used, etc.
 
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1.1.4 Features

GeoTIFF fully complies with the TIFF 6.0 specifications, and its extensions do not in any way go against the TIFF recommendations, nor do they limit the scope of raster data supported by TIFF.

GeoTIFF uses a small set of reserved TIFF tags to store a broad range of georeferencing information, catering to geographic as well as projected coordinate systems needs. Projections include UTM, US State Plane and National Grids, as well as the underlying projection types such as Transverse Mercator, Lambert Conformal Conic, etc. No information is stored in private structures, IFD's or other mechanisms which would hide information from naive TIFF reading software.

GeoTIFF uses a "MetaTag" (GeoKey) approach to encode dozens of information elements into just 6 tags, taking advantage of TIFF platform-independent data format representation to avoid cross-platform interchange difficulties. These keys are designed in a manner parallel to standard TIFF tags, and closely follow the TIFF discipline in their structure and layout. New keys may be defined as needs arise, within the current framework, and without requiring the allocation of new tags from Aldus/Adobe.

GeoTIFF uses numerical codes to describe projection types, coordinate systems, datums, ellipsoids, etc. The projection, datums and ellipsoid codes are derived from the EPSG list compiled by the Petrotechnical Open Software Corporation (POSC), and mechanisms for adding further international projections, datums and ellipsoids has been established. The GeoTIFF information content is designed to be compatible with the data decomposition approach used by the National Spatial Data Infrastructure (NSDI) of the U.S. Federal Geographic Data Committee (FGDC).

While GeoTIFF provides a robust framework for specifying a broad class of existing Projected coordinate systems, it is also fully extensible, permitting internal, private or proprietary information storage. However, since this standard arose from the need to avoid multiple proprietary encoding systems, use of private implementations is to be discouraged.
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1.2 Revision Notes

This is the final release of GeoTIFF Revision 1.0, supporting the new EPSG 2.x codes.

Changes from 1.8 document: minor spelling and typo corrections.

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1.2.1 Revision Nomenclature
A Revision of GeoTIFF specifications will be denoted by two integers separated by a decimal, indicating the Major and Minor revision numbers. GeoTIFF stores most of its information using a "Key-Code" pairing system; the Major revision number will only be incremented when a substantial addition or modification is made to the list of information Keys, while the Minor Revision number permits incremental augmentation of the list of valid codes.
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1.2.2 New Features
 
Revision 1.0 New Transformation Matrix Tag.
Index Table added in Section 6.4 to assist in looking up geodesy codes.
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1.2.3 Clarifications
Revision 1.0:

 o The former ModelTransformationTag (33920) conflicts with
   an internal Intergraph implementation and is being deprecated, 
   in favor of a new tag (34264, registered to JPL).

 o The "Origin" keys have been renamed with "Natural" or "Nat" 
   prefixes, to distinguish from "False" origins, and to have
   a closer match to EPSG/POSC terminology. All Revision 0.2
   names shall be recognized in a backward-compatible fashion.

 o The GeoTIFF/Cartlab web page addresses have been moved out
   of the author's ~ndr/ personal directory, and may now be found at:

    http://www-mipl.jpl.nasa.gov/cartlab/geotiff/geotiff.html

Revision 0.2:

 o South Oriented Gauss Conformal is Transverse Mercator with South
   pointing up, and so has been given a distinct code, rather than
   aliased to Transverse Mercator.

Revision 0.1:

 o GeoTIFF-writers shall store the GeoKey entries in key-sorted order
   within the GeoKeyDirectoryTag. This is a change from preliminary
   discussions which permitted arbitrary order, and more closely follows
   the TIFF discipline.

 o The third value "ScaleZ" in ModelPixelScaleTag = (ScaleX, ScaleY,
   ScaleZ) shall by default be set to 0, not 1, as suggested in preliminary
   discussions. This is because most standard model spaces are
   2-dimensional (flat), and therefore its vertical shape is 
   independent of the pixel-value.
 
 o The code 32767 shall be used to imply "user-defined", rather than
   16384. This avoids breaking up the reserved public GeoKey code space
   into two discontiguous ranges, 0-16383 and 16385-32767.
 
 o If a GeoKey is coded "undefined", then it is exactly that; no
   parameters should be provided (e.g. EllipsoidSemiMajorAxis, etc).
   To provide parameters for a non-coded attribute, use "user-defined".

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1.2.4 Organizational changes

None.
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1.2.5 Changes in Requirements
 Changes to this preliminary revision:

   o Support for new transformation matrix tag (34264) required.
  
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1.2.6 Agenda for Future Development

Revision 1.0, which is the first true "Baseline" revision, is proposed to support well-documented, public, relatively simple Projected Coordinate Systems (PCS), including most commonly used and supported in the international public domains today, together with their underlying map-projection systems. Following the critiques of the 0.x Revision phase, the 1.0 Revision spec is hereby released in Sept '95. 

In the coming year, incremental 1.x augmentations to the "codes" list will be established, as well as discussions regarding the future "2.0" requirements.

The Revision 2.0 phase is proposed to extend the capability of the GeoTIFF tagsets beyond PCS projections into more complex map projection geometries, including single-project, single-vendor, or proprietary cartographic solutions. 

TBD: Sounding Datums and related parameters for Digital Elevation Models (DEM's) and bathymetry -- Revision 2?

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1.3 Administration
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1.3.1 Information and Support:
The most recent version of the GeoTIFF spec, EPSG/POSC tables, and source code is available via anonymous FTP at:

       ftp://mtritter.jpl.nasa.gov/pub/tiff/geotiff/
and is mirrored at the USGS:

        ftp://ftpmcmc.cr.usgs.gov/release/geotiff/jpl_mirror/

   There are several subdirectories called spec/ tables/ and code/.

   The USGS also has an archive of prototype GeoTIFF images at:

        ftp://ftpmcmc.cr.usgs.gov/release/geotiff/images/

Information and a hypertext version of the GeoTIFF spec is available via WWW at the following site:

        http://www-mipl.jpl.nasa.gov/cartlab/geotiff/geotiff.html

A mailing-list is currently active to discuss the on-going development of this standard. To subscribe to this list, send e-mail to:

       GeoTIFF-request@tazboy.jpl.nasa.gov

with no subject and the body of the message reading:

     subscribe geotiff  your-name-here

To post inquiries directly to the list, send email to:

       geotiff@tazboy.jpl.nasa.gov

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1.3.2 Private Keys and Codes:
As with TIFF, in GeoTIFF private "GeoKeys" and codes may be used, starting with 32768 and above. Unlike the TIFF spec, however, these private key-spaces will not be reserved, and are only to be used for private, internal purposes. 
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1.3.3 Proposed Revisions to GeoTIFF
Should a feature arise which is not currently supported, it should be formally proposed for addition to the GeoTIFF spec, through the official mailing-list.

The current maintainer of the GeoTIFF specification is Niles Ritter, though this may change at a later time. Projection codes are maintained through EPSG/POSC, and a mechanism for change/additions will be established through the GeoTIFF mailing list. 

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2 Baseline GeoTIFF
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2.1 Notation
This spec follows the notation remarks of the TIFF 6.0 spec, regarding "is", "shall", "should", and "may"; the first two indicate mandatory requirements, "should" indicates a strong recommendation, while "may" indicates an option.
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2.2 GeoTIFF Design Considerations
Every effort has been made to adhere to the philosophy of TIFF data abstraction. The GeoTIFF tags conform to a hierarchical data structure of tags and keys, similar to the tags which have been implemented in the "basic" and "extended" TIFF tags already supported in TIFF Version 6 specification. The following are some points considered in the design of GeoTIFF:

o Private binary structures, while permitted under the TIFF spec, are in general difficult to maintain, and are intrinsically platform- dependent. Whenever possible, information should be sorted into their intrinsic data-types, and placed into appropriately named tags. Also, implementors of TIFF readers would be more willing to honor a new tag specification if it does not require parsing novel binary structures.

o Any Tag value which is to be used as a "keyword" switch or modifier should be a SHORT type, rather than an ASCII string. This avoids common mistakes of mis-spelling a keyword, as well as facilitating an implementation in code using the "switch/case" features of most languages. In general, scanning ASCII strings for keywords (CaseINSensitiVE?) is a hazardous (not to mention slower and more complex) operation.

o True "Extensibility" strongly suggests that the Tags defined have a sufficiently abstract definition so that the same tag and its values may be used and interpreted in different ways as more complex information spaces are developed. For example, the old SubFileType tag (255) had to be obsoleted and replaced with a NewSubFileType tag, because images began appearing which could not fit into the narrowly defined classes for that Tag. Conversely, the YCbCrSubsampling Tag has taken on new meaning and importance as the JPEG compression standard for TIFF becomes finalized.

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2.3 GeoTIFF Software Requirements
GeoTIFF requires support for all documented TIFF 6.0 tag data-types, and in particular requires the IEEE double-precision floating point "DOUBLE" type tag. Most of the parameters for georeferencing will not have sufficient accuracy with single-precision IEEE, nor with RATIONAL format storage. The only other alternative for storing high-precision values would be to encode as ASCII, but this does not conform to TIFF recommendations for data encoding.

It is worth emphasizing here that the TIFF spec indicates that TIFF-compliant readers shall honor the 'byte-order' indicator, meaning that 4-byte integers from files created on opposite order machines will be swapped in software, and that 8-byte DOUBLE's will be 8-byte swapped.

A GeoTIFF reader/writer, in addition to supporting the standard TIFF tag types, must also have an additional module which can parse the "Geokey" MetaTag information. A public-domain software package for performing this function is now available; see the "References" in section 5 for the location.

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2.4 GeoTIFF File and "Key" Structure

This section describes the abstract file-format and "GeoKey" data storage mechanism used in GeoTIFF. Uses of this mechanism for implementing georeferencing and geocoding is detailed in section 2.6 and section 2.7 .

A GeoTIFF file is a TIFF 6.0 file, and inherits the file structure as described in the corresponding portion of the TIFF spec. All GeoTIFF specific information is encoded in several additional reserved TIFF tags, and contains no private Image File Directories (IFD's), binary structures or other private information invisible to standard TIFF readers.
 
The number and type of parameters that would be required to describe most popular projection types would, if implemented as separate TIFF tags, likely require dozens or even hundred of tags, exhausting the limited resources of the TIFF tag-space. On the other hand, a private IFD, while providing thousands of free tags, is limited in that its tag-values are invisible to non-savvy TIFF readers (which don't know that the IFD_OFFSET tag value points to a private IFD).

To avoid these problems, a GeoTIFF file stores projection parameters in a set of "Keys" which are virtually identical in function to a "Tag", but has one more level of abstraction above TIFF. Effectively, it is a sort of "Meta-Tag". A Key works with formatted tag-values of a TIFF file the way that a TIFF file deals with the raw bytes of a data file. Like a tag, a Key has an ID number ranging from 0 to 65535, but unlike TIFF tags, all key ID's are available for use in GeoTIFF parameter definitions.

The Keys in GeoTIFF (also call "GeoKeys") are all referenced from the GeoKeyDirectoryTag, which defined as follows: 

GeoKeyDirectoryTag:
      Tag = 34735 (87AF.H) 
      Type = SHORT (2-byte unsigned short)
      N = variable, >= 4
      Alias: ProjectionInfoTag, CoordSystemInfoTag
      Owner: SPOT Image, Inc.

This tag may be used to store the GeoKey Directory, which defines and references the "GeoKeys", as described below. 

The tag is an array of unsigned SHORT values, which are primarily grouped into blocks of 4. The first 4 values are special, and contain GeoKey directory header information. The header values consist of the following information, in order:

  Header={KeyDirectoryVersion, KeyRevision, MinorRevision, NumberOfKeys}

  where 

     "KeyDirectoryVersion" indicates the current version of Key
     implementation, and will only change if this Tag's Key 
     structure is changed. (Similar to the TIFFVersion (42)).
     The current DirectoryVersion number is 1. This value will
     most likely never change, and may be used to ensure that
     this is a valid Key-implementation.
   
     "KeyRevision" indicates what revision of Key-Sets are used.

     "MinorRevision" indicates what set of Key-codes are used. The
     complete revision number is denoted <KeyRevision>.<MinorRevision>
          
     "NumberOfKeys" indicates how many Keys are defined by the rest
     of this Tag.
     
This header is immediately followed by a collection of <NumberOfKeys> KeyEntry sets, each of which is also 4-SHORTS long. Each KeyEntry is modeled on the "TIFFEntry" format of the TIFF directory header, and is of the form:

   KeyEntry = { KeyID, TIFFTagLocation, Count, Value_Offset }

   where 

     "KeyID" gives the key-ID value of the Key (identical in function
     to TIFF tag ID, but completely independent of TIFF tag-space),
     
     "TIFFTagLocation" indicates which TIFF tag contains the value(s)
      of the Key: if TIFFTagLocation is 0, then the value is SHORT,
      and is contained in the "Value_Offset" entry. Otherwise, the type
      (format) of the value is implied by the TIFF-Type of the tag
      containing the value.
  
     "Count" indicates the number of values in this key.
   
      "Value_Offset" Value_Offset indicates the index-
      offset *into* the TagArray indicated by TIFFTagLocation, if
      it is nonzero. If TIFFTagLocation=0, then Value_Offset
      contains the actual (SHORT) value of the Key, and
      Count=1 is implied. Note that the offset is not a byte-offset,
      but rather an index based on the natural data type of the
      specified tag array.  

Following the KeyEntry definitions, the KeyDirectory tag may also contain additional values. For example, if a Key requires multiple SHORT values, they shall be placed at the end of this tag, and the KeyEntry will set TIFFTagLocation=GeoKeyDirectoryTag, with the Value_Offset pointing to the location of the value(s).

All key-values which are not of type SHORT are to be stored in one of the following two tags, based on their format:

GeoDoubleParamsTag:
      Tag = 34736 (87BO.H) 
      Type = DOUBLE (IEEE Double precision)
      N = variable
      Owner: SPOT Image, Inc.

This tag is used to store all of the DOUBLE valued GeoKeys, referenced by the GeoKeyDirectoryTag. The meaning of any value of this double array is determined from the GeoKeyDirectoryTag reference pointing to it. FLOAT values should first be converted to DOUBLE and stored here.

GeoAsciiParamsTag:
      Tag = 34737 (87B1.H)  
      Type = ASCII
      Owner: SPOT Image, Inc.
      N = variable

This tag is used to store all of the ASCII valued GeoKeys, referenced by the GeoKeyDirectoryTag. Since keys use offsets into tags, any special comments may be placed at the beginning of this tag. For the most part, the only keys that are ASCII valued are "Citation" keys, giving documentation and references for obscure projections, datums, etc.

Note on ASCII Keys:

Special handling is required for ASCII-valued keys. While it is true that TIFF 6.0 permits multiple NULL-delimited strings within a single ASCII tag, the secondary strings might not appear in the output of naive "tiffdump" programs. For this reason, the null delimiter of each ASCII Key value shall be converted to a "|" (pipe) character before being installed back into the ASCII holding tag, so that a dump of the tag will look like this.

   AsciiTag="first_value|second_value|etc...last_value|"

A baseline GeoTIFF-reader must check for and convert the final "|" pipe character of a key back into a NULL before returning it to the client software. 

GeoKey Sort Order:

In the TIFF spec it is required that TIFF tags be written out to the file in tag-ID sorted order. This is done to avoid forcing software to perform N-squared sort operations when reading and writing tags.

To follow the TIFF philosophy, GeoTIFF-writers shall store the GeoKey entries in key-sorted order within the CoordSystemInfoTag.

Example:

  GeoKeyDirectoryTag=(   1,     1, 2,     6,
                      1024,     0, 1,     2,
                      1026, 34737,12,     0,
                      2048,     0, 1, 32767,
                      2049, 34737,14,    12,
                      2050,     0, 1,     6,
                      2051, 34736, 1,     0 )
  GeoDoubleParamsTag(34736)=(1.5)
  GeoAsciiParamsTag(34737)=("Custom File|My Geographic|")

The first line indicates that this is a Version 1 GeoTIFF GeoKey directory, the keys are Rev. 1.2, and there are 6 Keys defined in this tag.
The next line indicates that the first Key (ID=1024 = GTModelTypeGeoKey) has the value 2 (Geographic), explicitly placed in the entry list (since TIFFTagLocation=0). The next line indicates that the Key 1026 (the GTCitationGeoKey) is listed in the GeoAsciiParamsTag (34737) array, starting at offset 0 (the first in array), and running for 12 bytes and so has the value "Custom File" (the "|" is converted to a null delimiter at the end). Going further down the list, the Key 2051 (GeogLinearUnitSizeGeoKey) is located in the GeoDoubleParamsTag (34736), at offset 0 and has the value 1.5; the value of key 2049 (GeogCitationGeoKey) is "My Geographic".

The TIFF layer handles all the problems of data structure, platform independence, format types, etc, by specifying byte-offsets, byte-order format and count, while the Key describes its key values at the TIFF level by specifying Tag number, array-index, and count. Since all TIFF information occurs in TIFF arrays of some sort, we have a robust method for storing anything in a Key that would occur in a Tag.

With this Key-value approach, there are 65536 Keys which have all the flexibility of TIFF tag, with the added advantage that a TIFF dump will provide all the information that exists in the GeoTIFF implementation.

This GeoKey mechanism will be used extensively in section 2.7, where the numerous parameters for defining Coordinate Systems and their underlying projections are defined.
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2.5 Coordinate Systems in GeoTIFF
Geotiff has been designed so that standard map coordinate system definitions can be readily stored in a single registered TIFF tag. It has also been designed to allow the description of coordinate system definitions which are non-standard, and for the description of transformations between coordinate systems, through the use of three or four additional TIFF tags.
However, in order for the information to be correctly exchanged between various clients and providers of GeoTIFF, it is important to establish a common system for describing map projections.
In the TIFF/GeoTIFF framework, there are essentially three different spaces upon which coordinate systems may be defined. The spaces are:

  1) The raster space (Image space) R, used to reference the pixel values
     in an image,
  2) The Device space D, and
  3) The Model space, M, used to reference points on the earth.

In the sections that follow we shall discuss the relevance and use of each of these spaces, and their corresponding coordinate systems, from the standpoint of GeoTIFF.

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2.5.1 Device Space and GeoTIFF

In standard TIFF 6.0 there are tags which relate raster space R with device space D, such as monitor, scanner or printer. The list of such tags consists of the following:

    ResolutionUnit (296)
    XResolution    (282)
    YResolution    (283)
    Orientation    (274)
    XPosition      (286)
    YPosition      (287)

In Geotiff, provision is made to identify earth-referenced coordinate systems (model space M) and to relate M space with R space. This provision is independent of and can co-exist with the relationship between raster and device spaces. To emphasize the distinction, this spec shall not refer to "X" and "Y" raster coordinates, but rather to raster space "J" (row) and "I" (column) coordinate variables instead, as defined in section 2.5.2.2.

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2.5.2 Raster Coordinate Systems
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2.5.2.1 Raster Data

Raster data consists of spatially coherent, digitally stored numerical data, collected from sensors, scanners, or in other ways numerically derived. The manner in which this storage is implemented in a TIFF file is described in the standard TIFF specification. 

Raster data values, as read in from a file, are organized by software into two dimensional arrays, the indices of the arrays being used as coordinates. There may also be additional indices for multispectral data, but these indices do not refer to spatial coordinates but spectral, and so of not of concern here.

Many different types of raster data may be georeferenced, and there may be subtle ways in which the nature of the data itself influences how the coordinate system (Raster Space) is defined for raster data. For example, pixel data derived from imaging devices and sensors represent aggregate values collected over a small, finite, geographic area, and so it is natural to define coordinate systems in which the pixel value is thought of as filling an area. On the other hand, digital elevations models may consist of discrete "postings", which may best be considered as point measurements at the vertices of a grid, and not in the interior of a cell. 
2.5.2.2 Raster Space

The choice of origin for raster space is not entirely arbitrary, and depends upon the nature of the data collected. Raster space coordinates shall be referred to by their pixel types, i.e., as "PixelIsArea" or "PixelIsPoint".

Note: For simplicity, both raster spaces documented below use a fixed pixel size and spacing of 1. Information regarding the visual representation of this data, such as pixels with non-unit aspect ratios, scales, orientations, etc, are best communicated with the TIFF 6.0 standard tags.

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"PixelIsArea" Raster Space

The "PixelIsArea" raster grid space R, which is the default, uses coordinates I and J, with (0,0) denoting the upper-left corner of the image, and increasing I to the right, increasing J down. The first pixel-value fills the square grid cell with the bounds:

   top-left = (0,0), bottom-right = (1,1)

and so on; by extension this one-by-one grid cell is also referred to as a pixel. An N by M pixel image covers an are with the mathematically defined bounds (0,0),(N,M).

     (0,0)
      +---+---+-> I
      | * | * |
      +---+---+        Standard (PixelIsArea) TIFF Raster space R,
      | (1,1)  (2,1)      showing the areas (*) of several pixels.
      |
      J
      
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"PixelIsPoint" Raster Space

The PixelIsPoint raster grid space R uses the same coordinate axis names as used in PixelIsArea Raster space, with increasing I to the right, increasing J down. The first pixel-value however, is realized as a point value located at (0,0). An N by M pixel image consists of points which fill the mathematically defined bounds (0,0),(N-1,M-1).

     (0,0)   (1,0)
      *-------*------> I
      |       |
      |       |       PixelIsPoint TIFF Raster space R,
      *-------*         showing the location (*) of several pixels.
      |     (1,1)
      J

If a point-pixel image were to be displayed on a display device with pixel cells having the same size as the raster spacing, then the upper-left corner of the displayed image would be located in raster space at (-0.5, -0.5). 

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2.5.3 Model Coordinate Systems

The following methods of describing spatial model locations (as opposed to raster) are recognized in Geotiff: 
	Geographic coordinates
	Geocentric coordinates
	Projected coordinates
	Vertical coordinates

Geographic, geocentric and projected coordinates are all imposed on models of the earth. To describe a location uniquely, a coordinate set must be referenced to an adequately defined coordinate system. If a coordinate system is from the Geotiff standard definitions, the only reference required is the standard coordinate system code/name. If the coordinate system is non-standard, it must be defined. The required definitions are described below.

Projected coordinates, local grid coordinates, and (usually) geographical coordinates, form two dimensional horizontal coordinate systems (i.e., horizontal with respect to the earth's surface). Height is not part of these systems. To describe a position in three dimensions it is necessary to consider height as a second one dimensional vertical coordinate system.

To georeference an image in GeoTIFF, you must specify a Raster Space coordinate system, choose a horizontal model coordinate system, and a transformation between these two, as will be described in section 2.6

+----------------------------------+
2.5.3.1 Geographic Coordinate Systems

Geographic Coordinate Systems are those that relate angular latitude and longitude (and optionally geodetic height) to an actual point on the earth. The process by which this is accomplished is rather complex, and so we describe the components of the process in detail here.

+----------------------------------+
Ellipsoidal Models of the Earth

The geoid - the earth stripped of all topography - forms a reference surface for the earth. However, because it is related to the earth's gravity field, the geoid is a very complex surface; indeed, at a detailed level its description is not well known. The geoid is therefore not used in practical mapping.

It has been found that an oblate ellipsoid (an ellipse rotated about its minor axis) is a good approximation to the geoid and therefore a good model of the earth. Many approximations exist: several hundred ellipsoids have been defined for scientific purposes and about 30 are in day to day use for mapping. The size and shape of these ellipsoids can be defined through two parameters. Geotiff requires one of these to be
          the semi-major axis (a), 

and the second to be either 
          the inverse flattening (1/f) 
or 
          the semi-minor axis (b).

Historical models exist which use a spherical approximation; such models are not recommended for modern applications, but if needed the size of a model sphere may be defined by specifying identical values for the semimajor and semiminor axes; the inverse flattening cannot be used as it becomes infinite for perfect spheres.
Other ellipsoid parameters needed for mapping applications, for example the square of the eccentricity, can easily be calculated by an application from the two defining parameters. Note that Geotiff uses the modern geodesy convention for the symbol (b) for the semi-minor axis. No provision is made for mapping other planets in which a tri-dimensional (triaxial) ellipsoid might be required, where (b) would represent the semi-median axis and (c) the semi-minor axis.

Numeric codes for ellipsoids regularly used for earth-mapping are included in the Geotiff reference lists.

+----------------------------------+
Latitude and Longitude

The coordinate axes of the system referencing points on an ellipsoid are called latitude and longitude. More precisely, geodetic latitude and longitude are required in this Geotiff standard. A discussion of the several other types of latitude and longitude is beyond the scope of this document as they are not required for conventional mapping. 

Latitude is defined to be the angle subtended with the ellipsoid's equatorial plane by a perpendicular through the surface of the ellipsoid from a point. Latitude is positive if north of the equator, negative if south. 

Longitude is defined to be the angle measured about the minor (polar) axis of the ellipsoid from a prime meridian (see below) to the meridian through a point, positive if east of the prime meridian and negative if west. Unlike latitude which has a natural origin at the equator, there is no feature on the ellipsoid which forms a natural origin for the measurement of longitude. The zero longitude can be any defined meridian. Historically, nations have used the meridian through their national astronomical observatories, giving rise to several prime meridians. By international convention, the meridian through Greenwich, England is the standard prime meridian. Longitude is only unambiguous if the longitude of its prime meridian relative to Greenwich is given. Prime meridians other than Greenwich which are sometimes used for earth mapping are included in the Geotiff reference lists.

+----------------------------------+
Geodetic Datums

As well as there being several ellipsoids in use to model the earth, any one particular ellipsoid can have its location and orientation relative to the earth defined in different ways. If the relationship between the ellipsoid and the earth is changed, then the geographical coordinates of a point will change.

Conversely, for geographical coordinates to uniquely describe a location the relationship between the earth and the ellipsoid must be defined.  This relationship is described by a geodetic datum. An exact geodetic definition of geodetic datums is beyond the current scope of Geotiff. However the Geotiff standard requires that the geodetic datum being utilized be identified by numerical code. If required, defining parameters for the geodetic datum can be included as a citation.

+----------------------------------+
Defining Geographic Coordinate Systems

In summary, geographic coordinates are only unique if qualified by the code of the geographic coordinate system to which they belong. A geographic coordinate system has two axes, latitude and longitude, which are only unambiguous when both of the related prime meridian and geodetic datum are given, and in turn the geodetic datum definition includes the definition of an ellipsoid. The Geotiff standard includes a list of frequently used geographic coordinate systems and their component ellipsoids, geodetic datums and prime meridians. Within the Geotiff standard a geographic coordinate system can be identified either by 
           the code of a standard geographic coordinate system
or by
            a user-defined system.

The user is expected to provide geographic coordinate system code/name, geodetic datum code/name, ellipsoid code (if in standard) or ellipsoid name and two defining parameters (a) and either (1/f) or (b), and prime meridian code (if in standard) or name and longitude relative to Greenwich.

+----------------------------------+
2.5.3.2 Geocentric Coordinate Systems

A geocentric coordinate system is a 3-dimensional coordinate system with its origin at or near the center of the earth and with 3 orthogonal axes. The Z-axis is in or parallel to the earth's axis of rotation (or to the axis around which the rotational axis precesses). The X-axis is in or parallel to the plane of the equator and passes through its intersection with the Greenwich meridian, and the Y-axis is in the plane of the equator forming a right-handed coordinate system with the X and Z axes.

Geocentric coordinate systems are not frequently used for describing locations, but they are often utilized as an intermediate step when transforming between geographic coordinate systems. (Coordinate system transformations are described in section 2.6 below).

In the Geotiff standard, a geocentric coordinate system can be identified, either
	through the geographic code (which in turn implies a datum),
 or
	through a user-defined name.

+----------------------------------+
2.5.3.3 Projected Coordinate Systems

Although a geographical coordinate system is mathematically two dimensional, it describes a three dimensional object and cannot be represented on a plane surface without distortion. Map projections are transformations of geographical coordinates to plane coordinates in which the characteristics of the distortions are controlled. A map projection consists of a coordinate system transformation method and a set of defining parameters. A projected coordinate system (PCS) is a two dimensional (horizontal) coordinate set which, for a specific map projection, has a single and unambiguous transformation to a geographic coordinate system. 

In GeoTIFF PCS's are defined using the POSC/EPSG system, in which the PCS planar coordinate system, the Geographic coordinate system, and the transformation between them, are broken down into simpler logical components. Here are schematic formulas showing how the Projected Coordinate Systems and Geographic Coordinates Systems are encoded:

     Projected_CS  =  Geographic_CS + Projection
     Geographic_CS =  Angular_Unit + Geodetic_Datum + Prime_Meridian
     Projection    =  Linear Unit + Coord_Transf_Method + CT_Parameters 
     Coord_Transf_Method   = { TransverseMercator | LambertCC | ...}
     CT_Parameters = {OriginLatitude + StandardParallel+...}

(See also the Reference Parameters documentation in section 2.5.4). 
Notice that "Transverse Mercator" is not referred to as a "Projection", but rather as a "Coordinate Transformation Method"; in GeoTIFF, as in EPSG/POSC, the word "Projection" is reserved for particular, well-defined systems in which both the coordinate transformation method, its defining parameters, and their linear units are established. 

Several tens of coordinate transformation methods have been developed. Many are very similar and for practical purposes can be considered to give identical results. For example in the Geotiff standard Gauss-Kruger and Gauss-Boaga projection types are considered to be of the type Transverse Mercator. Geotiff includes a listing of commonly used projection defining parameters.

Different algorithms require different defining parameters. A future version of Geotiff will include formulas for specific map projection algorithms recommended for use with listed projection parameters.

To limit the magnitude of distortions of projected coordinate systems, the boundaries of usage are sometimes restricted. To cover more extensive areas, two or more projected coordinate systems may be required. In some cases many of the defining parameters of a set of projected coordinate systems will be held constant. 

The Geotiff standard does not impose a strict hierarchy onto such zoned systems such as US State Plane or UTM, but considers each zone to be a discrete projected coordinate system; the ProjectedCSTypeGeoKey code value alone is sufficient to identify the standard coordinate systems. 

Within the Geotiff standard a projected coordinate system can be identified either by 
        the code of a standard projected coordinate system 
or by
        a user-defined system. 

User-define projected coordinate systems may be defined by defining the Geographic Coordinate System, the coordinate transformation method and its associated parameters, as well as the planar system's linear units.

2.5.3.4 Vertical Coordinate Systems

Many uses of Geotiff will be limited to a two-dimensional, horizontal, description of location for which geographic coordinate systems and projected coordinate systems are adequate. If a three-dimensional description of location is required Geotiff allows this either through the use of a geocentric coordinate system or by defining a vertical coordinate system and using this together with a geographic or projected coordinate system.

In general usage, elevations and depths are referenced to a surface at or close to the geoid. Through increasing use of satellite positioning systems the ellipsoid is increasingly being used as a vertical reference surface. The relationship between the geoid and an ellipsoid is in general not well known, but is required when coordinate system transformations are to be executed.

+----------------------------------+
2.5.4 Reference Parameters

Most of the numerical coding systems and coordinate system definitions are based on the hierarchical system developed by EPSG/POSC. The complete set of EPSG tables used in GeoTIFF is available at:

  ftp://ftpmcmc.cr.usgs.gov/release/geotiff/jpl-mirror/tables
or:
     ftp://mtritter.jpl.nasa.gov/pub/tiff/geotiff/tables

Appended below is the README.TXT file that accompanies the tables of defining parameters for those codes:

                    +-----------------------------------+
                    |     EPSG Geodesy Parameters       |
                    |    version 2.1, 2nd June 1995.    |
                    +-----------------------------------+       

 The European Petroleum Survey Group (EPSG) has compiled and is
 distributing this set of parameters defining various geodetic
 and cartographic coordinate systems to encourage
 standardisation across the Exploration and Production segment
 of the oil industry.  The data is included as reference data
 in the Geotiff data exchange specification, in Iris21 the
 Petroconsultants data model, and in Epicentre, the POSC data
 model.  Parameters map directly to the POSC Epicentre model
 v2.0, except for data item codes which are included in the
 files for data management purposes.  Geodetic datum parameters
 are embedded within the geographic coordinate system file. 
 This has been done to ease parameter maintenance as there is a
 high correlation between geodetic datum names and geographic
 coordinate system names.  The Projected Coordinate System v2.0
 tabulation consists of systems associated with locally used
 projections.  Systems utilising the popular UTM grid system
 have also been included.
 
 Criteria used for material in these lists include:
   - information must be in the public domain: "private" data   
     is not included.
   - data must be in current use.
   - parameters are given to a precision consistent with
     coordinates being to a precision of one centimetre.
 
 The user assumes the entire risk as to the accuracy and the
 use of this data.  The data may be copied and distributed
 subject to the following conditions:
 
      1)   All data must then be copied without modification
 and all pages must be included;
           
      2)   All components of this data set must be distributed
 together;
           
      3)   The data may not be distributed for profit by any 
 third party; and
 
      4)   Acknowledgement to the original source must be
 given.
           
 INFORMATION  PROVIDED IN THIS DOCUMENT IS PROVIDED "AS IS"
 WITHOUT WARRANTY  OF  ANY  KIND,  EITHER  EXPRESSED OR 
 IMPLIED, INCLUDING  BUT  NOT LIMITED TO THE IMPLIED WARRANTIES
 OF MERCHANTABILITY AND/OR FITNESS FOR A PARTICULAR PURPOSE.
 
 Data is distributed on MS-DOS formatted diskette in comma-
 separated record format.  Additional copies may be obtained
 from Jean-Patrick Girbig at the address below at a cost of
 US$100 to cover media and shipping, payment to be made in
 favour of Petroconsultants S.A at Union Banque Suisses,
 1211 Geneve 11, Switzerland (compte number 403 458 60 K).
 
 The data is to be made available on a bulletin board shortly.

 Shipping List
 -------------
 
 This data set consists of 8 files:
 
 PROJCS.CSV  Tabulation of Projected Coordinate Systems to     
             which map grid coordinates may be referenced.
 
 GEOGCS.CSV  Tabulation of Geographic Coordinate Systems to    
             which latitude and longitude coordinates may be   
             referenced.  This table includes the equivalent   
             geocentric coordinate systems and also the        
             geodetic datum, reference to which allows latitude
             and longitude or geocentric XYZ to uniquely       
             describe a location on the earth.
 
 VERTCS.CSV  Tabulation of Vertical Coordinate Systems to     
             which heights or depths may be referenced. This
             table is currently in an early form.
 
 PROJ.CSV    Tabulation of transformation methods and          
             parameters through which Projected Coordinate     
             Systems are defined and related to Geographic     
             Coordinate Systems.
 
 ELLIPS.CSV  Tabulation of reference ellipsoids upon which     
             geodetic datums are based.
 
 PMERID.CSV  Tabulation of prime meridians upon which geodetic 
             datums are based.
 
 UNITS.CSV   Tabulation of length units used in Projected and  
             Vertical Coordinate Systems and angle units used  
             in Geographic Coordinate Systems.
 
 README.TXT  This file.

 

 

+---------------------------------------------------------------------+
2.6 Coordinate Transformations
The purpose of Geotiff is to allow the definitive identification of georeferenced locations within a raster dataset. This is generally accomplished through tying raster space coordinates to a model space coordinate system, when no further information is required. In the GeoTIFF nomenclature, "georeferencing" refers to tying raster space to a model space M, while "geocoding" refers to defining how the model space M assigns coordinates to points on the earth.
The three tags defined below may be used for defining the relationship between R and M, and the relationship may be diagrammed as:

           ModelPixelScaleTag 
           ModelTiepointTag         
    R  ------------ OR --------------> M
  (I,J,K)  ModelTransformationTag   (X,Y,Z) 

The next section describes these Baseline georeferencing tags in detail.

+----------------------------------+
2.6.1 GeoTIFF Tags for Coordinate Transformations
For most common applications, the transformation between raster and model space may be defined with a set of raster-to-model tiepoints and scaling parameters. The following two tags may be used for this purpose:

ModelTiepointTag:
      Tag = 33922 (8482.H) 
      Type = DOUBLE (IEEE Double precision)
      N = 6*K,  K = number of tiepoints
      Alias: GeoreferenceTag
      Owner: Intergraph

This tag stores raster->model tiepoint pairs in the order 

        ModelTiepointTag = (...,I,J,K, X,Y,Z...),

where (I,J,K) is the point at location (I,J) in raster space with pixel-value K, and (X,Y,Z) is a vector in model space. In most cases the model space is only two-dimensional, in which case both K and Z should be set to zero; this third dimension is provided in anticipation of future support for 3D digital elevation models and vertical coordinate systems. 

A raster image may be georeferenced simply by specifying its location, size and orientation in the model coordinate space M. This may be done by specifying the location of three of the four bounding corner points. However, tiepoints are only to be considered exact at the points specified; thus defining such a set of bounding tiepoints does not imply that the model space locations of the interior of the image may be exactly computed by a linear interpolation of these tiepoints.

However, since the relationship between the Raster space and the model space will often be an exact, affine transformation, this relationship can be defined using one set of tiepoints and the "ModelPixelScaleTag", described below, which gives the vertical and horizontal raster grid cell size, specified in model units. 

If possible, the first tiepoint placed in this tag shall be the one establishing the location of the point (0,0) in raster space. However, if this is not possible (for example, if (0,0) is goes to a part of model space in which the projection is ill-defined), then there is no particular order in which the tiepoints need be listed.

For orthorectification or mosaicking applications a large number of tiepoints may be specified on a mesh over the raster image. However, the definition of associated grid interpolation methods is not in the scope of the current GeoTIFF spec.

Remark: As mentioned in section 2.5.1, all GeoTIFF information is independent of the XPosition, YPosition, and Orientation tags of the standard TIFF 6.0 spec.

The next two tags are optional tags provided for defining exact affine transformations between raster and model space; baseline GeoTIFF files may use either, but shall never use both within the same TIFF image directory.

ModelPixelScaleTag:
      Tag = 33550
      Type = DOUBLE (IEEE Double precision)
      N = 3
      Owner: SoftDesk

This tag may be used to specify the size of raster pixel spacing in the model space units, when the raster space can be embedded in the model space coordinate system without rotation, and consists of the following 3 values:

    ModelPixelScaleTag = (ScaleX, ScaleY, ScaleZ)
    
where ScaleX and ScaleY give the horizontal and vertical spacing of raster pixels. The ScaleZ is primarily used to map the pixel value of a digital elevation model into the correct Z-scale, and so for most other purposes this value should be zero (since most model spaces are 2-D, with Z=0).

A single tiepoint in the ModelTiepointTag, together with this tag, completely determine the relationship between raster and model space; thus they comprise the two tags which Baseline GeoTIFF files most often will use to place a raster image into a "standard position" in model space.

Like the Tiepoint tag, this tag information is independent of the XPosition, YPosition, Resolution and Orientation tags of the standard TIFF 6.0 spec. However, simple reversals of orientation between raster and model space (e.g. horizontal or vertical flips) may be indicated by reversal of sign in the corresponding component of the ModelPixelScaleTag. GeoTIFF compliant readers must honor this sign-reversal convention.

This tag must not be used if the raster image requires rotation or shearing to place it into the standard model space. In such cases the transformation shall be defined with the more general ModelTransformationTag, defined below. 

ModelTransformationTag
      Tag  =  34264  (85D8.H) 
      Type =  DOUBLE    
      N    =  16
      Owner: JPL Cartographic Applications Group

This tag may be used to specify the transformation matrix between the raster space (and its dependent pixel-value space) and the (possibly 3D) model space. If specified, the tag shall have the following organization:

      ModelTransformationTag = (a,b,c,d,e....m,n,o,p).

where

        model                              image
        coords =          matrix     *     coords
        
        |-   -|     |-                 -|  |-   -|
        |  X  |     |   a   b   c   d   |  |  I  |
        |     |     |                   |  |     |
        |  Y  |     |   e   f   g   h   |  |  J  |
        |     |  =  |                   |  |     |
        |  Z  |     |   i   j   k   l   |  |  K  |
        |     |     |                   |  |     |
        |  1  |     |   m   n   o   p   |  |  1  |
        |-   -|     |-                 -|  |-   -|

By convention, and without loss of generality, the following parameters are currently hard-coded and will always be the same (but must be specified nonetheless):

       m = n = o = 0,  p = 1.

For Baseline GeoTIFF, the model space is always 2-D, and so the matrix will have the more limited form:

        |-   -|     |-                 -|  |-   -|
        |  X  |     |   a   b   0   d   |  |  I  |
        |     |     |                   |  |     |
        |  Y  |     |   e   f   0   h   |  |  J  |
        |     |  =  |                   |  |     |
        |  Z  |     |   0   0   0   0   |  |  K  |
        |     |     |                   |  |     |
        |  1  |     |   0   0   0   1   |  |  1  |
        |-   -|     |-                 -|  |-   -|

Values "d" and "h" will often be used to represent translations in  X and Y, and so will not necessarily be zero. All 16 values should be specified, in all cases. Only the raster-to-model transformation is defined; if the inverse transformation is required it must be computed by the client, to the desired accuracy.

This matrix tag should not be used if the ModelTiepointTag and the ModelPixelScaleTag are already defined. If only a single tiepoint (I,J,K,X,Y,Z) is specified, and the ModelPixelScale = (Sx, Sy, Sz) is specified, then the corresponding transformation matrix may be computed from them as:

        |-                         -| 
        |   Sx    0.0   0.0   Tx    | 
        |                           |      Tx = X - I/Sx
        |   0.0  -Sy    0.0   Ty    |      Ty = Y + J/Sy
        |                           |      Tz = Z - K/Sz  (if not 0)
        |   0.0   0.0   Sz    Tz    | 
        |                           | 
        |   0.0   0.0   0.0   1.0   | 
        |-                         -| 

where the -Sy is due the reversal of direction from J increasing- down in raster space to Y increasing-up in model space.
Like the Tiepoint tag, this tag information is independent of the XPosition, YPosition, and Orientation tags of the standard TIFF 6.0 spec.

Note: In Revision 0.2 and earlier, another tag was used for this matrix, which has been renamed as follows:
IntergraphMatrixTag
      Tag  =  33920  (8480.H) 
      Type =  DOUBLE    
      N    =  17 (Intergraph implementation) or 16 (GeoTIFF 0.2 impl.)
      Owner: Intergraph

This tag conflicts with an internal software implementation at Intergraph, and so its use is no longer encouraged. A GeoTIFF reader should look first for the new tag, and only if it is not found should it check for this older tag. If found, it should only consider it to be contain valid GeoTIFF matrix information if the tag-count is 16; the Intergraph version uses 17 values.

+----------------------------------+
2.6.2 Coordinate Transformation Data Flow

The dataflow of the various GeoTIFF parameter datasets is based upon the EPSG/POSC configuration. Here is the text of the description accompanying the EPSG parameter tables:

The data files (.CSV) have a hierarchical structure:
 
 +---------------------------+   +----------------------------+
 |           VERTCS          |   |           PROJCS           |
 +---------------------------+   +----------------------------+
 |Vertical Coordinate Systems|   |Projected Coordinate Systems|
 +-------------+-------------+   +------------+---------------+
               |                              |
      +--------+                              |
      |                                       |
      |            +--------------------------+
      |            |                          |
      |            |            +-------------+---------------+
      |            |            |            GEOGCS           |
      |            |            +-----------------------------+
      |            |            |Geographic Coordinate Systems|
      |            |            |Geocentric Coordinate Systems|
      |            |            +-----------------------------+
      |            |            |       Geodetic Datums       |
      |            |            +-------------+---------------+
      |            |                          |
      |            |                 +--------+-------+
      |            |                 |                |    
      |     +------+-----+    +------+-----+   +------+-------+
      |     |    PROJ    |    |   ELLIPS   |   |    PMERID    |
      |     +------------+    +------------+   +--------------+
      |     | Projection |    | Ellipsoid  |   |Prime Meridian|
      |     | Parameters |    | Parameters |   |  Parameters  |
      |     +------+-----+    +------+-----+   +------+-------+
      |            |                 |                |
      +------------+-----------+-----+----------------+         
                               |                          
                 +-------------+------------+
                 |           UNITS          |
                 +--------------------------+
                 | Linear and Angular Units |
                 +--------------------------+

 The parameter listings are "living documents" and will be
 updated by the EPSG from time to time. Any comment or
 suggestions for improvements should be directed to:
 
   Jean-Patrick Girbig,      or   Roger Lott,
   Manager Cartography,           Head of Survey,
   Petroconsultants S.A.,         BP Exploration,
   PO Box 152,                    Uxbridge One,
   24 Chemin de la Marie,         Harefield Road,
   1258 Perly-Geneva,             Uxbridge,
   Switzerland.                   Middlesex UB8 1PD,
                                  England.
                                 
                                  Internet:
                                   lottrj@txpcap.hou.xwh.bp.com
 
 Requests for the inclusion of new data should include supporting 
 documentation.  Requests for changing existing data should include 
 reference to both the name and code of the item.

+----------------------------------+
2.6.3 Cookbook for Defining Transformations

Here is a 4-step guide to producing a set of Baseline GeoTIFF tags for defining coordinate transformation information of a raster dataset. 
  
  Step 1: Establish the Raster Space coordinate system used: 
          RasterPixelIsArea or RasterPixelIsPoint.
  
  Step 2: Establish/define the model space Type in which the image is
          to be georeferenced. Usually this will be a Projected 
          Coordinate system (PCS). If you are geocoding this data
          set, then the model space is defined to be the corresponding
          geographic, geocentric or Projected coordinate system (skip 
          to the "Cookbook" section 2.7.3 first to do determine this).
          
  Step 3: Identify the nature of the transformations needed to tie
          the raster data down to the model space coordinate system:
          
     Case 1: The model-location of a raster point (x,y) is known, but not
          the scale or orientations:
     
            Use the ModelTiepointTag to define the (X,Y,Z) coordinates
            of the known raster point.

     Case 2: The location of three non-collinear raster points are known
          exactly, but the linearity of the transformation is not known.
         
          Use the ModelTiepointTag to define the (X,Y,Z) coordinates
          of all three known raster points. Do not compute or define the 
          ModelPixelScale or ModelTransformation tag.
         
     Case 3: The position and scale of the data is known exactly, and
          no rotation or shearing is needed to fit into the model space.
          
          Use the ModelTiepointTag to define the (X,Y,Z) coordinates
          of the known raster point, and the ModelPixelScaleTag to
          specify the scale.
          
     Case 4: The raster data requires rotation and/or lateral shearing to
          fit into the defined model space:
          
          Use the ModelTransformation matrix to define the transformation.
          
     Case 5: The raster data cannot be fit into the model space with a
          simple affine transformation (rubber-sheeting required).
          
          Use only the ModelTiepoint tag, and specify as many
          tiepoints as your application requires. Note, however, that
          this is not a Baseline GeoTIFF implementation, and should
          not be used for interchange; it is recommended that the image be
          geometrically rectified first, and put into a standard projected
          coordinate system.

   Step 4: Install the defined tag values in the TIFF file and close it.

+----------------------------------+
2.7 Geocoding Raster Data
+----------------------------------+
2.7.1 General Approach
A geocoded image is a georeferenced image as described in section 2.6, which also specifies a model space coordinate system (CS) between the model space M (to which the raster space has been tied) and the earth. The relationship can be diagrammed, including the associated TIFF tags, as follows:
        ModelPixelScaleTag 
        ModelTiepointTag                  GeoKeyDirectoryTag CS 
    R  -------- OR ---------------> M  --------- AND  -----------> Earth
        ModelTransformationTag            GeoDoubleParamsTag  
                                          GeoAsciiParamsTag  

The geocoding coordinate system is defined by the GeoKeyDirectoryTag, while the Georeferencing information (T) is defined by the ModelTiepointTag and the ModelPixelScale, or ModelTransformationTag. Since these two systems are independent of each other, the tags used to store the parameters are separated from each other in the GeoTIFF file to emphasize the orthogonality. 

+----------------------------------+
2.7.2 GeoTIFF GeoKeys for Geocoding
As mentioned above, all information regarding the Model Coordinate System used in the raster data is referenced from the GeoKeyDirectoryTag, which stores all of the GeoKey entries. In the Appendix, section 6.2 summarizes all of the GeoKeys defined for baseline GeoTIFF, and their corresponding codes are documented in section 6.3. Only the Keys themselves are documented here.

+----------------------------------+
Common Features
+----------------------------------+
     
Public and Private Key and Code Ranges

GeoTIFF GeoKey ID's may take any value between 0 and 65535. Following TIFF general approach, the GeoKey ID's from 32768 and above are available for private implementations. However, no registry will be established for these keys or codes, so developers are warned to use them at their own risk.

The Key ID's from 0 to 32767 are reserved for use by the official GeoTIFF spec, and are broken down into the following sub-domains:

   [    0,  1023]       Reserved
   [ 1024,  2047]       GeoTIFF Configuration Keys
   [ 2048,  3071]       Geographic/Geocentric CS Parameter Keys
   [ 3072,  4095]       Projected CS Parameter Keys
   [ 4096,  5119]       Vertical CS Parameter Keys
   [ 5120, 32767]       Reserved
   [32768, 65535]       Private use

GeoKey codes, like keys and tags, also range from 0 to 65535. Following the TIFF approach, all codes from 32768 and above are available for private user implementation. There will be no registry for these codes, however, and so developers must be sure that these tags will only be used internally. Use private codes at your own risk.

The codes from 0 to 32767 for all public GeoKeys are reserved by this GeoTIFF specification.

Common Public Code Values

For consistency, several key codes have the same meaning in all implemented GeoKeys possessing a SHORT numerical coding system:

          0 = undefined
      32767 = user-defined

The "undefined" code means that this parameter is intentionally omitted, for whatever reason. For example, the datum used for a given map may be unknown, or the accuracy of a aerial photo is so low that to specify a particular datum would imply a higher accuracy than is in the data.

The "user-defined" code means that a feature is not among the standard list, and is being explicitly defined. In cases where this is meaningful, Geokey parameters have been supplied for the user to define this feature.

"User-Defined" requirements: In each section below a specification of the additional GeoKeys required for the "user-defined" option is given. In all cases the corresponding "Citation" key is strongly recommended, as per the FGDC Metadata standard regarding "local" types.

+----------------------------------+
GeoTIFF Configuration GeoKeys
+----------------------------------+

These keys are to be used to establish the general configuration of this file's coordinate system, including the types of raster coordinate systems, model coordinate systems, and citations if any.

+---------------------------------------------------------------------+
GTModelTypeGeoKey      
Key ID = 1024
Type: SHORT (code)
Values: Section 6.3.1.1 Codes

This GeoKey defines the general type of model Coordinate system used, and to which the raster space will be transformed:unknown, Geocentric (rarely used), Geographic, Projected Coordinate System, or user-defined. If the coordinate system is a PCS, then only the PCS code need be specified. If the coordinate system does not fit into one of the standard registered PCS'S, but it uses one of the standard projections and datums, then its should be documented as a PCS model with "user-defined" type, requiring the specification of projection parameters, etc. 

GeoKey requirements for User-Defined Model Type (not advisable):

     GTCitationGeoKey

+---------------------------------------------------------------------+
GTRasterTypeGeoKey       
Key ID = 1025  
Type = Section 6.3.1.2 codes

This establishes the Raster Space coordinate system used; there are currently only two, namely RasterPixelIsPoint and RasterPixelIsArea. No user-defined raster spaces are currently supported. For variance in imaging display parameters, such as pixel aspect-ratios, use the standard TIFF 6.0 device-space tags instead.

+---------------------------------------------------------------------+
GTCitationGeoKey       
Key ID = 1026  
Type = ASCII

As with all the "Citation" GeoKeys, this is provided to give an ASCII reference to published documentation on the overall configuration of this GeoTIFF file.

+---------------------------------------------------------------------+
+----------------------------------+
Geographic CS Parameter GeoKeys
+----------------------------------+
+---------------------------------------------------------------------+

In general, the geographic coordinate system used will be implied by the projected coordinate system code. If however, this is a user-defined PCS, or the ModelType was chosen to be Geographic, then the system must be explicitly defined here, using the Horizontal datum code.

+---------------------------------------------------------------------+
GeographicTypeGeoKey    
Key ID = 2048  
Type = SHORT (code)
Values = Section 6.3.2.1 Codes    

This key may be used to specify the code for the geographic coordinate system used to map lat-long to a specific ellipsoid over the earth.

GeoKey Requirements for User-Defined geographic CS:
 
       GeogCitationGeoKey
       GeogGeodeticDatumGeoKey
 	GeogAngularUnitsGeoKey (if not degrees)
	GeogPrimeMeridianGeoKey (if not Greenwich)

+---------------------------------------------------------------------+
GeogCitationGeoKey
Key ID = 2049
Type = ASCII
Values = text

General citation and reference for all Geographic CS parameters.
+---------------------------------------------------------------------+
GeogGeodeticDatumGeoKey    
Key ID = 2050  
Type = SHORT (code)
Values = Section 6.3.2.2 Codes    

This key may be used to specify the horizontal datum, defining the size, position and orientation of the reference ellipsoid used in user-defined geographic coordinate systems.

GeoKey Requirements for User-Defined Horizontal Datum: 
       GeogCitationGeoKey
       GeogEllipsoidGeoKey

+---------------------------------------------------------------------+
GeogPrimeMeridianGeoKey
Key ID = 2051
Type = SHORT (code)
Units: Section 6.3.2.4 code

Allows specification of the location of the Prime meridian for user-defined geographic coordinate systems. The default standard is Greenwich, England.
+---------------------------------------------------------------------+
GeogPrimeMeridianLongGeoKey
Key ID = 2061  
Type = DOUBLE 
Units =  GeogAngularUnits

This key allows definition of user-defined Prime Meridians, the location of which is defined by its longitude relative to Greenwich.

+---------------------------------------------------------------------+
GeogLinearUnitsGeoKey 
Key ID = 2052
Type = DOUBLE
Values: Section 6.3.1.3 Codes

Allows the definition of geocentric CS linear units for user-defined GCS.

+---------------------------------------------------------------------+
GeogLinearUnitSizeGeoKey 
Key ID = 2053
Type = DOUBLE
Units: meters

Allows the definition of user-defined linear geocentric units, as measured in meters.
+---------------------------------------------------------------------+
GeogAngularUnitsGeoKey
Key ID = 2054  
Type = SHORT (code)
Values =  Section 6.3.1.4  Codes 

Allows the definition of geocentric CS Linear units for user-defined GCS and for ellipsoids.

GeoKey Requirements for "user-defined" units:
    GeogCitationGeoKey
    GeogAngularUnitSizeGeoKey 
+---------------------------------------------------------------------+
GeogAngularUnitSizeGeoKey 
Key ID = 2055
Type = DOUBLE
Units: radians

Allows the definition of user-defined angular geographic units, as measured in radians.
+---------------------------------------------------------------------+
GeogEllipsoidGeoKey
Key ID = 2056
Type = SHORT (code)
Values = Section 6.3.2.3 Codes 
   
This key may be used to specify the coded ellipsoid used in the geodetic datum of the Geographic Coordinate System. 

GeoKey Requirements for User-Defined Ellipsoid: 

   GeogCitationGeoKey
   [GeogSemiMajorAxisGeoKey, 
           [GeogSemiMinorAxisGeoKey | GeogInvFlatteningGeoKey] ]

+---------------------------------------------------------------------+
GeogSemiMajorAxisGeoKey  
Key ID = 2057
Type = DOUBLE
Units: Geocentric CS Linear Units

Allows the specification of user-defined Ellipsoid Semi-Major Axis (a). 

+---------------------------------------------------------------------+
GeogSemiMinorAxisGeoKey  
Key ID = 2058
Type = DOUBLE
Units: Geocentric CS Linear Units

Allows the specification of user-defined Ellipsoid Semi-Minor Axis (b). 

+---------------------------------------------------------------------+
GeogInvFlatteningGeoKey
Key ID = 2059
Type = DOUBLE
Units: none.

Allows the specification of the inverse of user-defined Ellipsoid's flattening parameter (f). The eccentricity-squared e^2 of the ellipsoid is related to the non-inverted f by:

      e^2  = 2*f  - f^2
 
   Note: if the ellipsoid is spherical the inverse-flattening
   becomes infinite; use the GeogSemiMinorAxisGeoKey instead, and
   set it equal to the semi-major axis length.

+---------------------------------------------------------------------+
GeogAzimuthUnitsGeoKey
Key ID = 2060  
Type = SHORT (code)
Values =  Section 6.3.1.4 Codes 

This key may be used to specify the angular units of measurement used to defining azimuths, in geographic coordinate systems. These may be used for defining azimuthal parameters for some projection algorithms, and may not necessarily be the same angular units used for lat-long.

+---------------------------------------------------------------------+

+----------------------------------+
Projected CS Parameter GeoKeys
+----------------------------------+

The PCS range of GeoKeys includes the projection and coordinate transformation keys as well. The projection keys are included in this block since they can only be used to define projected coordinate systems.
+---------------------------------------------------------------------+
ProjectedCSTypeGeoKey   
Key ID = 3072
Type = SHORT (codes)
Values: Section 6.3.3.1 codes

This code is provided to specify the projected coordinate system.

GeoKey requirements for "user-defined" PCS families:
   PCSCitationGeoKey
   ProjectionGeoKey

 +---------------------------------------------------------------------+
PCSCitationGeoKey
Key ID = 3073
Type = ASCII

As with all the "Citation" GeoKeys, this is provided to give an ASCII reference to published documentation on the Projected  Coordinate System particularly if this is a "user-defined" PCS.

+---------------------------------------------------------------------+

+----------------------------------+
Projection Definition GeoKeys
+----------------------------------+
+---------------------------------------------------------------------+

With the exception of the first two keys, these are mostly  projection-specific parameters, and only a few will be required for any particular projection type. Projected coordinate systems automatically imply a specific projection type, as well as specific parameters for that projection, and so the keys below will only be necessary for user-defined projected coordinate systems.
+---------------------------------------------------------------------+
ProjectionGeoKey
Key ID = 3074
Type = SHORT (code)
Values:  Section 6.3.3.2 codes

Allows specification of the coordinate transformation method and projection zone parameters.  Note : when associated with an appropriate Geographic Coordinate System, this forms a Projected Coordinate System.

GeoKeys Required for "user-defined" Projections:

   PCSCitationGeoKey
   ProjCoordTransGeoKey
   ProjLinearUnitsGeoKey
   (additional parameters depending on ProjCoordTransGeoKey).

+---------------------------------------------------------------------+
ProjCoordTransGeoKey
Key ID = 3075
Type = SHORT (code)
Values:  Section 6.3.3.3 codes

Allows specification of the coordinate transformation method used. Note: this does not include the definition of the corresponding Geographic Coordinate System to which the projected CS is related; only the transformation method is defined here.

GeoKeys Required for "user-defined" Coordinate Transformations:

   PCSCitationGeoKey
   <additional parameter geokeys depending on the Coord. Trans. specified).

+---------------------------------------------------------------------+
ProjLinearUnitsGeoKey
Key ID = 3076 
Type = SHORT (code)
Values: Section 6.3.1.3 codes 

Defines linear units used by this projection.
+---------------------------------------------------------------------+
ProjLinearUnitSizeGeoKey
Key ID = 3077 
Type = DOUBLE
Units: meters

Defines size of user-defined linear units in meters.
+---------------------------------------------------------------------+
ProjStdParallel1GeoKey
Key ID = 3078 
Type = DOUBLE
Units: GeogAngularUnit 
Alias: ProjStdParallelGeoKey (from Rev 0.2)

Latitude of primary Standard Parallel.
+---------------------------------------------------------------------+
ProjStdParallel2GeoKey
Key ID = 3079
Type = DOUBLE
Units: GeogAngularUnit 

Latitude of second Standard Parallel.
+---------------------------------------------------------------------+
ProjNatOriginLongGeoKey
Key ID = 3080
Type = DOUBLE
Units: GeogAngularUnit 
Alias: ProjOriginLongGeoKey

Longitude of map-projection Natural origin. 
+---------------------------------------------------------------------+
ProjNatOriginLatGeoKey
Key ID = 3081
Type = DOUBLE
Units: GeogAngularUnit
Alias: ProjOriginLatGeoKey

Latitude of map-projection Natural origin.
+---------------------------------------------------------------------+
ProjFalseEastingGeoKey
Key ID = 3082
Type = DOUBLE
Units: ProjLinearUnit 

Gives the easting coordinate of the map projection Natural origin.
+---------------------------------------------------------------------+
ProjFalseNorthingGeoKey
Key ID = 3083
Type = DOUBLE
Units: ProjLinearUnit 

Gives the northing coordinate of the map projection Natural origin.
+---------------------------------------------------------------------+
ProjFalseOriginLongGeoKey
Key ID = 3084
Type = DOUBLE
Units: GeogAngularUnit 

Gives the longitude of the False origin.
+---------------------------------------------------------------------+
ProjFalseOriginLatGeoKey
Key ID = 3085
Type = DOUBLE
Units: GeogAngularUnit 

Gives the latitude of the False origin.
+---------------------------------------------------------------------+
ProjFalseOriginEastingGeoKey
Key ID = 3086
Type = DOUBLE
Units: ProjLinearUnit 

Gives the easting coordinate of the false origin. This is NOT the False Easting, which is the easting attached to the Natural origin.
+---------------------------------------------------------------------+
ProjFalseOriginNorthingGeoKey
Key ID = 3087
Type = DOUBLE
Units: ProjLinearUnit 

Gives the northing coordinate of the False origin. This is NOT the False Northing, which is the northing attached to the Natural origin.
+---------------------------------------------------------------------+
ProjCenterLongGeoKey
Key ID = 3088
Type = DOUBLE
Units: GeogAngularUnit 

Longitude of Center of Projection. Note that this is not necessarily the origin of the projection.
+---------------------------------------------------------------------+
ProjCenterLatGeoKey
Key ID = 3089
Type = DOUBLE
Units: GeogAngularUnit

Latitude of Center of Projection. Note that this is not necessarily the origin of the projection.
+---------------------------------------------------------------------+
ProjCenterEastingGeoKey
Key ID = 3090
Type = DOUBLE
Units: ProjLinearUnit 

Gives the easting coordinate of the center. This is NOT the False Easting.
+---------------------------------------------------------------------+
ProjFalseOriginNorthingGeoKey
Key ID = 3091
Type = DOUBLE
Units: ProjLinearUnit 

Gives the northing coordinate of the center. This is NOT the False Northing.
+---------------------------------------------------------------------+
ProjScaleAtNatOriginGeoKey
Key ID = 3092
Type = DOUBLE
Units: none
Alias: ProjScaleAtOriginGeoKey (Rev. 0.2)

Scale at Natural Origin. This is a ratio, so no units are required.
+---------------------------------------------------------------------+
ProjScaleAtCenterGeoKey
Key ID = 3093 
Type = DOUBLE
Units: none

Scale at Center. This is a ratio, so no units are required.
+---------------------------------------------------------------------+
ProjAzimuthAngleGeoKey
Key ID = 3094
Type = DOUBLE
Units: GeogAzimuthUnit
 
Azimuth angle east of true north of the central line passing through the projection center (for elliptical (Hotine) Oblique Mercator). Note that this is the standard method of measuring azimuth, but is opposite the usual mathematical convention of positive indicating counter-clockwise.
+---------------------------------------------------------------------+
ProjStraightVertPoleLongGeoKey   
Key ID = 3095 
Type = DOUBLE
Units: GeogAngularUnit 

Longitude at Straight Vertical Pole. For polar stereographic.
+---------------------------------------------------------------------+
GeogAzimuthUnitsGeoKey
Key ID = 2060  
Type = SHORT (code)
Values =  Section 6.3.1.4 Codes 

This key is actually part of the "Geographic CS Parameter Keys" section, but is mentioned here as it is useful for defining units used in the azimuthal projection parameters.

+---------------------------------------------------------------------+

+----------------------------------+
Vertical CS Parameter Keys
+----------------------------------+

Note: Vertical coordinate systems are not yet implemented. These sections are provided for future development, and any vertical coordinate systems in the current revision must be defined using the VerticalCitationGeoKey.
+---------------------------------------------------------------------+
VerticalCSTypeGeoKey
Key ID = 4096  
Type = SHORT (code)
Values =  Section 6.3.4.1  Codes 

This key may be used to specify the vertical coordinate system.
+---------------------------------------------------------------------+
VerticalCitationGeoKey
Key ID = 4097
Type = ASCII
Values =  text 

This key may be used to document the vertical coordinate system used, and its parameters.
+---------------------------------------------------------------------+
VerticalDatumGeoKey
Key ID = 4098   
Type = SHORT (code)
Values =  Section 6.3.4.2  codes

This key may be used to specify the vertical datum for the vertical coordinate system.

+---------------------------------------------------------------------+
VerticalUnitsGeoKey
Key ID = 4099   
Type = SHORT (code)
Values =  Section 6.3.1.3  Codes 

This key may be used to specify the vertical units of measurement used in the geographic coordinate system, in cases where geographic CS's need to reference the vertical coordinate. This, together with the Citation key, comprise the only fully implemented keys in this section, at present.

+----------------------------------+
2.7.3 Cookbook for Geocoding Data

Step 1: Determine the Coordinate system type of the raster data, based on
        the nature of the data: pixels derived from scanners or other 
        optical devices represent areas, and most commonly will use the
        RasterPixelIsArea coordinate system. Pixel data such as digital
        elevation models represent points, and will probably use 
        RasterPixelIsPoint coordinates.

           Store in: GTRasterTypeGeoKey

Step 2: Determine which class of model space coordinates are most natural
        for this dataset:Geographic, Geocentric, or Projected Coordinate 
        System. Usually this will be PCS.
        
           Store in: GTModelTypeGeoKey
           
Step 3: This step depends on the GTModelType:

      case PCS:  Determine the PCS projection system. Most of the
           PCS's used in standard State Plane and national grid systems
           are defined, so check this list first; the EPSG index in 
           section 6.4 may be useful for this purpose.
               
           Store in: ProjectedCSTypeGeoKey, ProjectedCSTypeGeoKey

           If coded, it will not be necessary to specify the Projection 
           datum, etc for this case, since all of those parameters
           are determined by the ProjectedCSTypeGeoKey code. Skip to
           step 4 from here.
               
           If none of the coded PCS's match your system, then this is a
           user-defined PCS. Use the Projection code list to check for
           standard projection systems.

           Store in: ProjectionGeoKey and skip to Geographic CS case.

           If none of the Projection codes match your system, then this
           is a user-defined projection. Use the ProjCoordTransGeoKey to
           specify the coordinate transformation method (e.g. Transverse
           Mercator), and all of the associated parameters of that method.
           Also define the linear units used in the planar coordinate
           system.
           
           Store in: ProjCoordTransGeoKey, ProjLinearUnitsGeoKey  
               <and other CT related parameter keys>

           Now continue on to define the Geographic CS, below.

      case GEOCENTRIC:
      case GEOGRAPHIC:  Check the list of standard GCS's and use the
           corresponding code. To use a code both the Datum, Prime
           Meridian, and angular units must match those of the code.
                
           Store in:  GeographicTypeGeoKey and skip to Step 4.

           If none of the coded GCS's match exactly, then this is a
           user-defined GCS. Check the list of standard datums,
           Prime Meridians, and angular units to define your system.

           Store in: GeogGeodeticDatumGeoKey, GeogAngularUnitsGeoKey,
              GeogPrimeMeridianGeoKey and skip to Step 4. 
  
           If none of the datums match your system, you have a 
           user-defined datum, which is an odd system, indeed. Use 
           the GeogEllipsoidGeoKey to select the appropriate ellipsoid
           or use the GeogSemiMajorAxisGeoKey, GeogInvFlatteningGeoKey to 
           define, and give a reference using the GeogCitationGeoKey.

           Store in: GeogEllipsoidGeoKey, etc. and go to Step 4.

Step 4: Install the GeoKeys/codes into the GeoKeyDirectoryTag, and the
      DOUBLE and ASCII key values into the corresponding value-tags.
      
Step 5: Having completely defined the Raster & Model coordinate system,
      go to Cookbook section 2.6.2 and use the Georeferencing Tags
      to tie the raster image down onto the Model space.

+----------------------------------+
3  Examples
+----------------------------------+

Here are some examples of how GeoTIFF may be implemented at the  Tag and GeoKey level, following the general "Cookbook" approach above. 

+----------------------------------+
3.1 Common Examples

+----------------------------------+
3.1.1. UTM Projected Aerial Photo
   
We have an aerial photo which has been orthorectified and resampled to a UTM grid, zone 60, using WGS84 datum; the coordinates of the upper-left corner of the image is are given in easting/northing, as 350807.4m, 5316081.3m. The scanned map pixel scale is 100 meters/pixels (the actual dpi scanning ratio is irrelevant).
   
      ModelTiepointTag       = (0, 0, 0,  350807.4, 5316081.3, 0.0)
      ModelPixelScaleTag      = (100.0, 100.0, 0.0)
      GeoKeyDirectoryTag:
            GTModelTypeGeoKey        =  1      (ModelTypeProjected)
            GTRasterTypeGeoKey       =  1      (RasterPixelIsArea)
            ProjectedCSTypeGeoKey    =  32660  (PCS_WGS84_UTM_zone_60N)
            PCSCitationGeoKey        =  "UTM Zone 60 N with WGS84"

   Notes:

   1) We did not need to specify the GCS lat-long, since the 
      PCS_WGS84_UTM_zone_60N codes implies particular 
      GCS and units already (WGS_84 and meters). The citation
      was added just for documentation.
 
   2)  The "GeoKeyDirectoryTag" is expressed using the "GeoKey" 
   structure defined above. At the TIFF level the tags look like
   this:

      GeoKeyDirectoryTag=(  1,     0,     2,       4,
                         1024,     0,     1,       1,
                         1025,     0,     1,       1,
                         3072,     0,     1,       32660,
                         3073, 34737,    25,       0 ) 
      GeoAsciiParamsTag(34737)=("UTM Zone 60 N with WGS84|")
      
   For the rest of these examples we will only show the GeoKey-level
   dump, with the understanding that the actual TIFF-level tag
   representation can be determined from the documentation.

+----------------------------------+
3.1.2. Standard State Plane
      
We have a USGS State Plane Map of Texas, Central Zone, using NAD83, correctly oriented. The map resolution is 1000 meters/pixel, at origin. There is a grid intersection line in the image at pixel location (50,100), and corresponds to the projected coordinate system easting/northing of (949465.0, 3070309.1).
      
      ModelTiepointTag           = (  50,  100, 0, 949465.0, 3070309.1, 0)   
      ModelPixelScaleTag         = (1000, 1000, 0)
      GeoKeyDirectoryTag:
            GTModelTypeGeoKey            =  1   (ModelTypeProjected)
            GTRasterTypeGeoKey           =  1   (RasterPixelIsArea)
            ProjectedCSTypeGeoKey        = 32139 (PCS_NAD83_Texas_Central)

    Notice that in this case, since the PCS is a standard code, we
    do not need to define the GCS, datum, etc, since those are implied
    by the PCS code. Also, since this is NAD83, meters are used rather
    than US Survey feet (as in NAD 27).

  
+----------------------------------+
3.1.3. Lambert Conformal Conic Aeronautical Chart
      
We have a 500 x 500 scanned aeronautical chart of Seattle, WA, using Lambert Conformal Conic projection, correctly oriented. The central meridian is at 120 degrees west. The map resolution is 1000 meters/pixel, at origin, and uses NAD27 datum. The standard parallels of the projection are at 41d20m N and 48d40m N. The latitude of the origin is at 45 degrees North, and occurs in the image at the raster coordinates (80,100). The origin is given a false easting and northing of 200000m, 1500000m.
      
      ModelTiepointTag          = (  80,  100, 0,  200000,  1500000,  0)   
      ModelPixelScaleTag         = (1000, 1000, 0)
      GeoKeyDirectoryTag:
            GTModelTypeGeoKey               =  1     (ModelTypeProjected)
            GTRasterTypeGeoKey              =  1     (RasterPixelIsArea)
            GeographicTypeGeoKey            =  4267  (GCS_NAD27)
            ProjectedCSTypeGeoKey           =  32767 (user-defined)
            ProjectionGeoKey                =  32767 (user-defined)
            ProjLinearUnitsGeoKey           =  9001     (Linear_Meter)
            ProjCoordTransGeoKey            =  8  (CT_LambertConfConic_2SP)
                 ProjStdParallel1GeoKey     =  41.333
                 ProjStdParallel2GeoKey     =  48.666
                 ProjCenterLongGeoKey       =-120.0
                 ProjNatOriginLatGeoKey     =  45.0
                 ProjFalseEastingGeoKey,    = 200000.0
                 ProjFalseNorthingGeoKey,   = 1500000.0

   Notice that the Tiepoint takes the false easting and northing into
   account when tying the raster point (50,100) to the projection origin.

   

+--------------------------------------------------------------------+
3.1.4. DMA ADRG Raster Graphic Map

The U.S. Defense Mapping Agency produces ARC digitized raster graphics datasets by scanning maps and geometrically resampling them into an equirectangular projection, so that they may be directly indexed with WGS84 geographic coordinates. The scale for one map is 0.2 degrees per pixel horizontally, 0.1 degrees per pixel vertically. If stored in a GeoTIFF file it contains the following information:  

      ModelTiepointTag=(0.0, 0.0, 0.0,  -120.0,       32.0,     0.0)
      ModelPixelScale = (0.2, 0.1, 0.0) 
      GeoKeyDirectoryTag:
            GTModelTypeGeoKey          =  2   (ModelTypeGeographic)
            GTRasterTypeGeoKey         =  1   (RasterPixelIsArea)
            GeographicTypeGeoKey       =  4326 (GCS_WGS_84)
 
+----------------------------------+
3.2 Less Common Examples

+----------------------------------+
3.2.1. Unrectified Aerial photo, known tiepoints, in degrees.
   
We have an aerial photo, and know only the WGS84 GPS location of several points in the scene: the upper left corner is 120 degrees West, 32 degrees North, the lower-left corner is at 120 degrees West, 30 degrees 20 minutes North, and the lower-right hand corner of the image is at 116 degrees 40 minutes  West, 30 degrees 20 minutes North. The  photo is not geometrically corrected, however, and the complete projection is therefore not known.
   
    ModelTiepointTag=(   0.0,    0.0, 0.0,  -120.0,       32.0,     0.0,
                         0.0, 1000.0, 0.0,  -120.0,       30.33333, 0.0,
                      1000.0, 1000.0, 0.0,  -116.6666667, 30.33333, 0.0) 
      GeoKeyDirectoryTag:
            GTModelTypeGeoKey          =   1 (ModelTypeGeographic)
            GTRasterTypeGeoKey         =   1 (RasterPixelIsArea)
            GeographicTypeGeoKey       = 4326 (GCS_WGS_84)
            
    Remark: Since we have not specified the ModelPixelScaleTag, clients
       reading this GeoTIFF file are not permitted to infer that there
       is a simple linear relationship between the raster data and the
       geographic model coordinate space. The only points that are know
       to be exact are the ones specified in the tiepoint tag.   

+----------------------------------+
3.2.2. Rotated Scanned Map
   
We have a scanned standard British National Grid, covering the 100km grid zone NZ. Consulting documentation for BNG we find that the southwest corner of the NZ zone has an easting,northing of 400000m, 500000m, relative to the BNG standard false origin. This scanned map has a resolution of 100 meter pixels, and was rotated 90 degrees to fit onto the scanner, so that the southwest corner is now the northwest corner. In this case we must use the ModelTransformation tag rather than the tiepoint/scale pair to map the raster data into model space:
   
      ModelTransformationTag  = (     0, 100.0,     0,   400000.0,
                                  100.0,     0,     0,   500000.0,
                                      0,     0,     0,          0,
                                      0,     0,     0,          1)
      GeoKeyDirectoryTag:
            GTModelTypeGeoKey        =  1 ( ModelTypeProjected)
            GTRasterTypeGeoKey       =  1  (RasterPixelIsArea)
            ProjectedCSTypeGeoKey    =  27700 (PCS_British_National_Grid)
            PCSCitationGeoKey        =  "British National Grid, Zone NZ"

Remark: the matrix has 100.0 in the off-diagonals due to the 90 degree rotation; increasing I points north, and increasing J points east.
      
+----------------------------------+
3.2.3. Digital Elevation Model
The DMA stores digital elevation models using an equirectangular projection, so that it may be indexed with WGS84 geographic coordinates. Since elevation postings are point-values, the pixels should not be considered as filling areas, but as point-values at grid vertices. To accommodate the base elevation of the Angeles Crest forest, the pixel value of 0 corresponds to an elevation of 1000 meters relative to WGS84 reference ellipsoid. The upper left corner is at 120 degrees West, 32 degrees North, and has a pixel scale of 0.2 degrees/pixel longitude, 0.1 degrees/pixel latitude.

      ModelTiepointTag=(0.0, 0.0, 0.0,  -120.0,       32.0,    1000.0)
      ModelPixelScale = (0.2, 0.1, 1.0) 
      GeoKeyDirectoryTag:
            GTModelTypeGeoKey          =  2     (ModelTypeGeographic)
            GTRasterTypeGeoKey         =  2     (RasterPixelIsPoint)
            GeographicTypeGeoKey       =  4326  (GCS_WGS_84)
            VerticalCSTypeGeoKey       =  5030  (VertCS_WGS_84_ellipsoid)
            VerticalCitationGeoKey     =  "WGS 84 Ellipsoid"
            VerticalUnitsGeoKey        =  9001     (Linear_Meter)

   Remarks: 
          1) Note the "RasterPixelIsPoint" raster space, indicating that
             the DEM posting of the first pixel is at the raster point
             (0,0,0), and therefore corresponds to 120W,32N exactly.
          2) The third value of the "PixelScale" is 1.0 to indicate
             that a single pixel-value unit corresponds to 1 meter,
             and the last tiepoint value indicates that base value
             zero indicates 1000m above the reference surface.

+----------------------------------+
4 Extended GeoTIFF
+--------------------------------------------------------------------+

This section is for future development TBD.

Possible additional GeoKeys for Revision 2.0:

   PerspectHeightGeoKey   (General Vertical Nearsided Perspective)
   SOMInclinAngleGeoKey   (SOM)
   SOMAscendLongGeoKey    (SOM)
   SOMRevPeriodGeoKey     (SOM)
   SOMEndOfPathGeoKey     (SOM)  ? is this needed ?  SHORT
   SOMRatioGeoKey         (SOM)
   SOMPathNumGeoKey       (SOM)    SHORT
   SOMSatelliteNumGeoKey  (SOM)    SHORT
   OEAShapeMGeoKey        (Oblated Equal Area)
   OEAShapeNGeoKey        (Oblated Equal Area)
   OEARotationAngleGeoKey (Oblated Equal Area)

Other items for consideration:

o Digital Elevation Model information, such as Vertical Datums, Sounding Datums.

o Accuracy Keys for linear, circular, and spherical errors, etc.

o Source information, such as details of an original coordinate system 
  and of transformations between it and the coordinate system in which 
  data is being exchanged.

+--------------------------------------------------------------------+
5 References
+--------------------------------------------------------------------+
 1. EPSG/POSC Projection Coding System Tables. Available via FTP to:

     ftp://mtritter.jpl.nasa.gov/pub/tiff/geotiff/tables
    
    or its USGS mirror site:

      ftp://ftpmcmc.cr.usgs.gov/release/geotiff/jpl-mirror/tables

 2. TIFF Revision 6.0 Specification: A PDF formatted version
    is available via FTP to:

ftp://ftp.adobe.com/pub/adobe/DeveloperSupport/TechNotes/PDFfiles/TIFF6.pdf

     PostScript formatted text versions available at:.

       ftp://sgi.com/graphics/tiff/TIFF6.ps.Z   (compressed)
       ftp://sgi.com/graphics/tiff/TIFF6.ps     (uncompressed)

 3. LIBGEOTIFF -- Public Domain GeoTIFF library, available via anonymous
    FTP to:

      ftp://mtritter.jpl.nasa.gov/pub/tiff/geotiff/code

   or its USGS mirror site:

      ftp://ftpmcmc.cr.usgs.gov/release/geotiff/jpl-mirror/code

 4. LIBTIFF -- Public Domain TIFF library, available via anonymous
    FTP to:

      ftp://sgi.com/graphics/tiff/

 5. Spatial Data Transfer Standard (SDTS) of the USGS.
   (Federal Information Processing Standard (FIPS) 173):

      ftp://sdts.er.usgs.gov/pub/sdts/
 
        SDTS Task Force
        U.S. Geological Survey
        526 National Center
        Reston, VA 22092 
        
        E-mail: sdts@usgs.gov 

 6. Map use: reading, analysis, interpretation.
       Muehrcke, Phillip C. 1986. Madison, WI: JP Publications. 

 7. Map projections: a working manual. Snyder, John P. 1987. 
    USGS Professional Paper 1395.
    Washington, DC: United States Government Printing Office. 

 8. Notes for GIS and The Geographer's Craft at U. Texas, on the 
    World Wide Web (WWW) (current as of 10 April 1995):

     http://wwwhost.cc.utexas.edu/ftp/pub/grg/gcraft/notes/notes.html

 9. Digital Geographic Information Exchange Standard (DIGEST).
     Allied Geographic Publication No 3, Edition 1.2 (AGeoP-3)
     (NATO Unclassified).

10. POSC Petrotechnical Open Software Corporation Web site:  

      http://www.posc.org/

+--------------------------------------------------------------------+
6 Appendices
+--------------------------------------------------------------------+

+----------------------------------+
6.1 Tag ID Summary

Here are all of the TIFF tags (and their owners) that are used to store GeoTIFF information of any type. It is very unlikely that any other tags will be necessary in the future (since most additional information will be encoded as a GeoKey).

    ModelPixelScaleTag     = 33550 (SoftDesk)
    ModelTransformationTag = 34264 (JPL Carto Group)
    ModelTiepointTag       = 33922 (Intergraph)
    GeoKeyDirectoryTag     = 34735 (SPOT)
    GeoDoubleParamsTag     = 34736 (SPOT)
    GeoAsciiParamsTag      = 34737 (SPOT)

  Obsoleted Implementation:
 
    IntergraphMatrixTag = 33920 (Intergraph) -- Use ModelTransformationTag.
  
+----------------------------------+
6.2 Key ID Summary
+----------------------------------+

+----------------------------------+
6.2.1 GeoTIFF Configuration Keys

   GTModelTypeGeoKey            = 1024 /* Section 6.3.1.1 Codes       */
   GTRasterTypeGeoKey           = 1025 /* Section 6.3.1.2 Codes       */
   GTCitationGeoKey             = 1026 /* documentation */

+----------------------------------+
6.2.2 Geographic CS Parameter Keys
   GeographicTypeGeoKey         = 2048 /* Section 6.3.2.1 Codes     */
   GeogCitationGeoKey           = 2049 /* documentation             */
   GeogGeodeticDatumGeoKey      = 2050 /* Section 6.3.2.2 Codes     */
   GeogPrimeMeridianGeoKey      = 2051 /* Section 6.3.2.4 codes     */
   GeogLinearUnitsGeoKey        = 2052 /* Section 6.3.1.3 Codes     */
   GeogLinearUnitSizeGeoKey     = 2053 /* meters                    */
   GeogAngularUnitsGeoKey       = 2054 /* Section 6.3.1.4 Codes     */
   GeogAngularUnitSizeGeoKey    = 2055 /* radians                   */
   GeogEllipsoidGeoKey          = 2056 /* Section 6.3.2.3 Codes     */
   GeogSemiMajorAxisGeoKey      = 2057 /* GeogLinearUnits           */
   GeogSemiMinorAxisGeoKey      = 2058 /* GeogLinearUnits           */
   GeogInvFlatteningGeoKey      = 2059 /* ratio                     */
   GeogAzimuthUnitsGeoKey       = 2060 /* Section 6.3.1.4 Codes     */
   GeogPrimeMeridianLongGeoKey  = 2061 /* GeogAngularUnit           */
    
+----------------------------------+
6.2.3 Projected CS Parameter Keys

   ProjectedCSTypeGeoKey          = 3072  /* Section 6.3.3.1 codes   */
   PCSCitationGeoKey              = 3073  /* documentation           */
   ProjectionGeoKey               = 3074  /* Section 6.3.3.2 codes   */
   ProjCoordTransGeoKey           = 3075  /* Section 6.3.3.3 codes   */
   ProjLinearUnitsGeoKey          = 3076  /* Section 6.3.1.3 codes   */
   ProjLinearUnitSizeGeoKey       = 3077  /* meters                  */
   ProjStdParallel1GeoKey         = 3078  /* GeogAngularUnit */
   ProjStdParallel2GeoKey         = 3079  /* GeogAngularUnit */
   ProjNatOriginLongGeoKey        = 3080  /* GeogAngularUnit */
   ProjNatOriginLatGeoKey         = 3081  /* GeogAngularUnit */
   ProjFalseEastingGeoKey         = 3082  /* ProjLinearUnits */
   ProjFalseNorthingGeoKey        = 3083  /* ProjLinearUnits */
   ProjFalseOriginLongGeoKey      = 3084  /* GeogAngularUnit */
   ProjFalseOriginLatGeoKey       = 3085  /* GeogAngularUnit */
   ProjFalseOriginEastingGeoKey   = 3086  /* ProjLinearUnits */
   ProjFalseOriginNorthingGeoKey  = 3087  /* ProjLinearUnits */
   ProjCenterLongGeoKey           = 3088  /* GeogAngularUnit */
   ProjCenterLatGeoKey            = 3089  /* GeogAngularUnit */
   ProjCenterEastingGeoKey        = 3090  /* ProjLinearUnits */
   ProjCenterNorthingGeoKey       = 3091  /* ProjLinearUnits */
   ProjScaleAtNatOriginGeoKey     = 3092  /* ratio   */
   ProjScaleAtCenterGeoKey        = 3093  /* ratio   */
   ProjAzimuthAngleGeoKey         = 3094  /* GeogAzimuthUnit */
   ProjStraightVertPoleLongGeoKey = 3095  /* GeogAngularUnit */

Aliases:

   ProjStdParallelGeoKey	= ProjStdParallel1GeoKey
   ProjOriginLongGeoKey	= ProjNatOriginLongGeoKey 
   ProjOriginLatGeoKey	= ProjNatOriginLatGeoKey  
   ProjScaleAtOriginGeoKey	= ProjScaleAtNatOriginGeoKey

 

+----------------------------------+
6.2.4 Vertical CS Keys
   
   VerticalCSTypeGeoKey           = 4096   /* Section 6.3.4.1 codes   */
   VerticalCitationGeoKey         = 4097   /* documentation */
   VerticalDatumGeoKey            = 4098   /* Section 6.3.4.2 codes   */
   VerticalUnitsGeoKey            = 4099   /* Section 6.3.1.3 codes   */

+---------------------------------------------------------------------+
+----------------------------------+
6.3 Key Code Summary
+----------------------------------+
6.3.1 GeoTIFF General Codes
This section includes the general "Configuration" key codes, as well as general codes which are used by more than one key (e.g. units codes).
+----------------------------------+
6.3.1.1 Model Type Codes

Ranges:

   0              = undefined
   [   1,  32766] = GeoTIFF Reserved Codes
   32767          = user-defined
   [32768, 65535] = Private User Implementations

GeoTIFF defined CS Model Type Codes:

   ModelTypeProjected   = 1   /* Projection Coordinate System         */
   ModelTypeGeographic  = 2   /* Geographic latitude-longitude System */
   ModelTypeGeocentric  = 3   /* Geocentric (X,Y,Z) Coordinate System */
 
Notes:

   1. ModelTypeGeographic and ModelTypeProjected
      correspond to the FGDC metadata Geographic and
      Planar-Projected coordinate system types.

+----------------------------------+
6.3.1.2 Raster Type Codes
Ranges:

   0             = undefined
   [   1,  1023] = Raster Type Codes (GeoTIFF Defined)
   [1024, 32766] = Reserved
   32767         = user-defined
   [32768, 65535]= Private User Implementations

Values:
   RasterPixelIsArea  = 1
   RasterPixelIsPoint = 2

Note: Use of "user-defined" or "undefined" raster codes is not recommended.

+----------------------------------+
6.3.1.3 Linear Units Codes

There are several different kinds of units that may be used in geographically related raster data: linear units, angular units, units of time (e.g. for radar-return), CCD-voltages, etc. For this reason there will be a single, unique range for each kind of unit, broken down into the following currently defined ranges:

Ranges:

   0             = undefined
   [   1,  2000] = Obsolete GeoTIFF codes
   [2001,  8999] = Reserved by GeoTIFF
   [9000,  9099] = EPSG Linear Units.
   [9100,  9199] = EPSG Angular Units.
   32767         = user-defined unit
   [32768, 65535]= Private User Implementations

Linear Unit Values (See the ESPG/POSC tables for definition):

   Linear_Meter =	9001
   Linear_Foot =	9002
   Linear_Foot_US_Survey =	9003
   Linear_Foot_Modified_American =	9004
   Linear_Foot_Clarke =	9005
   Linear_Foot_Indian =	9006
   Linear_Link =	9007
   Linear_Link_Benoit =	9008
   Linear_Link_Sears =	9009
   Linear_Chain_Benoit =	9010
   Linear_Chain_Sears =	9011
   Linear_Yard_Sears =	9012
   Linear_Yard_Indian =	9013
   Linear_Fathom =	9014
   Linear_Mile_International_Nautical =	9015

+----------------------------------+
6.3.1.4 Angular Units Codes
These codes shall be used for any key that requires specification of an angular unit of measurement.

Angular Units    

   Angular_Radian =	9101
   Angular_Degree =	9102
   Angular_Arc_Minute =	9103
   Angular_Arc_Second =	9104
   Angular_Grad =	9105
   Angular_Gon =	9106
   Angular_DMS =	9107
   Angular_DMS_Hemisphere =	9108

+----------------------------------+
6.3.2 Geographic CS Codes

+----------------------------------+
6.3.2.1 Geographic CS Type Codes

Note: A Geographic coordinate system consists of both a datum and a Prime Meridian. Some of the names are very similar, and differ only in the Prime Meridian, so be sure to use the correct one. The codes beginning with GCSE_xxx are unspecified GCS which use ellipsoid (xxx); it is recommended that only the codes beginning with GCS_ be used if possible.
Ranges:
     
   0 = undefined
   [    1,  1000] = Obsolete EPSG/POSC Geographic Codes
   [ 1001,  3999] = Reserved by GeoTIFF
   [ 4000, 4199]  = EPSG GCS Based on Ellipsoid only
   [ 4200, 4999]  = EPSG GCS Based on EPSG Datum
   [ 5000, 32766] = Reserved by GeoTIFF
   32767          = user-defined GCS
   [32768, 65535] = Private User Implementations

Values:

  Note: Geodetic datum using Greenwich PM have codes equal to
  the corresponding Datum code - 2000.

   GCS_Adindan =	4201
   GCS_AGD66 =	4202
   GCS_AGD84 =	4203
   GCS_Ain_el_Abd =	4204
   GCS_Afgooye =	4205
   GCS_Agadez =	4206
   GCS_Lisbon =	4207
   GCS_Aratu =	4208
   GCS_Arc_1950 =	4209
   GCS_Arc_1960 =	4210
   GCS_Batavia =	4211
   GCS_Barbados =	4212
   GCS_Beduaram =	4213
   GCS_Beijing_1954 =	4214
   GCS_Belge_1950 =	4215
   GCS_Bermuda_1957 =	4216
   GCS_Bern_1898 =	4217
   GCS_Bogota =	4218
   GCS_Bukit_Rimpah =	4219
   GCS_Camacupa =	4220
   GCS_Campo_Inchauspe =	4221
   GCS_Cape =	4222
   GCS_Carthage =	4223
   GCS_Chua =	4224
   GCS_Corrego_Alegre =	4225
   GCS_Cote_d_Ivoire =	4226
   GCS_Deir_ez_Zor =	4227
   GCS_Douala =	4228
   GCS_Egypt_1907 =	4229
   GCS_ED50 =	4230
   GCS_ED87 =	4231
   GCS_Fahud =	4232
   GCS_Gandajika_1970 =	4233
   GCS_Garoua =	4234
   GCS_Guyane_Francaise =	4235
   GCS_Hu_Tzu_Shan =	4236
   GCS_HD72 =	4237
   GCS_ID74 =	4238
   GCS_Indian_1954 =	4239
   GCS_Indian_1975 =	4240
   GCS_Jamaica_1875 =	4241
   GCS_JAD69 =	4242
   GCS_Kalianpur =	4243
   GCS_Kandawala =	4244
   GCS_Kertau =	4245
   GCS_KOC =	4246
   GCS_La_Canoa =	4247
   GCS_PSAD56 =	4248
   GCS_Lake =	4249
   GCS_Leigon =	4250
   GCS_Liberia_1964 =	4251
   GCS_Lome =	4252
   GCS_Luzon_1911 =	4253
   GCS_Hito_XVIII_1963 =	4254
   GCS_Herat_North =	4255
   GCS_Mahe_1971 =	4256
   GCS_Makassar =	4257
   GCS_EUREF89 =	4258
   GCS_Malongo_1987 =	4259
   GCS_Manoca =	4260
   GCS_Merchich =	4261
   GCS_Massawa =	4262
   GCS_Minna =	4263
   GCS_Mhast =	4264
   GCS_Monte_Mario =	4265
   GCS_M_poraloko =	4266
   GCS_NAD27 =	4267
   GCS_NAD_Michigan =	4268
   GCS_NAD83 =	4269
   GCS_Nahrwan_1967 =	4270
   GCS_Naparima_1972 =	4271
   GCS_GD49 =	4272
   GCS_NGO_1948 =	4273
   GCS_Datum_73 =	4274
   GCS_NTF =	4275
   GCS_NSWC_9Z_2 =	4276
   GCS_OSGB_1936 =	4277
   GCS_OSGB70 =	4278
   GCS_OS_SN80 =	4279
   GCS_Padang =	4280
   GCS_Palestine_1923 =	4281
   GCS_Pointe_Noire =	4282
   GCS_GDA94 =	4283
   GCS_Pulkovo_1942 =	4284
   GCS_Qatar =	4285
   GCS_Qatar_1948 =	4286
   GCS_Qornoq =	4287
   GCS_Loma_Quintana =	4288
   GCS_Amersfoort =	4289
   GCS_RT38 =	4290
   GCS_SAD69 =	4291
   GCS_Sapper_Hill_1943 =	4292
   GCS_Schwarzeck =	4293
   GCS_Segora =	4294
   GCS_Serindung =	4295
   GCS_Sudan =	4296
   GCS_Tananarive =	4297
   GCS_Timbalai_1948 =	4298
   GCS_TM65 =	4299
   GCS_TM75 =	4300
   GCS_Tokyo =	4301
   GCS_Trinidad_1903 =	4302
   GCS_TC_1948 =	4303
   GCS_Voirol_1875 =	4304
   GCS_Voirol_Unifie =	4305
   GCS_Bern_1938 =	4306
   GCS_Nord_Sahara_1959 =	4307
   GCS_Stockholm_1938 =	4308
   GCS_Yacare =	4309
   GCS_Yoff =	4310
   GCS_Zanderij =	4311
   GCS_MGI =	4312
   GCS_Belge_1972 =	4313
   GCS_DHDN =	4314
   GCS_Conakry_1905 =	4315
   GCS_WGS_72 =	4322
   GCS_WGS_72BE =	4324
   GCS_WGS_84 =	4326
   GCS_Bern_1898_Bern =	4801
   GCS_Bogota_Bogota =	4802
   GCS_Lisbon_Lisbon =	4803
   GCS_Makassar_Jakarta =	4804
   GCS_MGI_Ferro =	4805
   GCS_Monte_Mario_Rome =	4806
   GCS_NTF_Paris =	4807
   GCS_Padang_Jakarta =	4808
   GCS_Belge_1950_Brussels =	4809
   GCS_Tananarive_Paris =	4810
   GCS_Voirol_1875_Paris =	4811
   GCS_Voirol_Unifie_Paris =	4812
   GCS_Batavia_Jakarta =	4813
   GCS_ATF_Paris =	4901
   GCS_NDG_Paris =	4902

Ellipsoid-Only GCS:

   Note: the numeric code is equal to the code of the correspoding
   EPSG ellipsoid, minus 3000.

   GCSE_Airy1830 =	4001
   GCSE_AiryModified1849 =	4002
   GCSE_AustralianNationalSpheroid =	4003
   GCSE_Bessel1841 =	4004
   GCSE_BesselModified =	4005
   GCSE_BesselNamibia =	4006
   GCSE_Clarke1858 =	4007
   GCSE_Clarke1866 =	4008
   GCSE_Clarke1866Michigan =	4009
   GCSE_Clarke1880_Benoit =	4010
   GCSE_Clarke1880_IGN =	4011
   GCSE_Clarke1880_RGS =	4012
   GCSE_Clarke1880_Arc =	4013
   GCSE_Clarke1880_SGA1922 =	4014
   GCSE_Everest1830_1937Adjustment =	4015
   GCSE_Everest1830_1967Definition =	4016
   GCSE_Everest1830_1975Definition =	4017
   GCSE_Everest1830Modified =	4018
   GCSE_GRS1980 =	4019
   GCSE_Helmert1906 =	4020
   GCSE_IndonesianNationalSpheroid =	4021
   GCSE_International1924 =	4022
   GCSE_International1967 =	4023
   GCSE_Krassowsky1940 =	4024
   GCSE_NWL9D =	4025
   GCSE_NWL10D =	4026
   GCSE_Plessis1817 =	4027
   GCSE_Struve1860 =	4028
   GCSE_WarOffice =	4029
   GCSE_WGS84 =	4030
   GCSE_GEM10C =	4031
   GCSE_OSU86F =	4032
   GCSE_OSU91A =	4033
   GCSE_Clarke1880 =	4034
   GCSE_Sphere =	4035

+----------------------------------+
6.3.2.2 Geodetic Datum Codes
Note: these codes do not include the Prime Meridian; if possible use the GCS codes above if the datum and Prime Meridian are on the list. Also, as with the GCS codes, the codes beginning with DatumE_xxx refer only to the specified ellipsoid (xxx); if possible use instead the named datums beginning with Datum_xxx
Ranges:, 

   0 = undefined
   [    1,  1000] = Obsolete EPSG/POSC Datum Codes
   [ 1001,  5999] = Reserved by GeoTIFF
   [ 6000, 6199]  = EPSG Datum Based on Ellipsoid only
   [ 6200, 6999]  = EPSG Datum Based on EPSG Datum
   [ 6322, 6327]  = WGS Datum
   [ 6900, 6999]  = Archaic Datum
   [ 7000, 32766] = Reserved by GeoTIFF
   32767          = user-defined GCS
   [32768, 65535] = Private User Implementations

Values:

   Datum_Adindan =	6201
   Datum_Australian_Geodetic_Datum_1966 =	6202
   Datum_Australian_Geodetic_Datum_1984 =	6203
   Datum_Ain_el_Abd_1970 =	6204
   Datum_Afgooye =	6205
   Datum_Agadez =	6206
   Datum_Lisbon =	6207
   Datum_Aratu =	6208
   Datum_Arc_1950 =	6209
   Datum_Arc_1960 =	6210
   Datum_Batavia =	6211
   Datum_Barbados =	6212
   Datum_Beduaram =	6213
   Datum_Beijing_1954 =	6214
   Datum_Reseau_National_Belge_1950 =	6215
   Datum_Bermuda_1957 =	6216
   Datum_Bern_1898 =	6217
   Datum_Bogota =	6218
   Datum_Bukit_Rimpah =	6219
   Datum_Camacupa =	6220
   Datum_Campo_Inchauspe =	6221
   Datum_Cape =	6222
   Datum_Carthage =	6223
   Datum_Chua =	6224
   Datum_Corrego_Alegre =	6225
   Datum_Cote_d_Ivoire =	6226
   Datum_Deir_ez_Zor =	6227
   Datum_Douala =	6228
   Datum_Egypt_1907 =	6229
   Datum_European_Datum_1950 =	6230
   Datum_European_Datum_1987 =	6231
   Datum_Fahud =	6232
   Datum_Gandajika_1970 =	6233
   Datum_Garoua =	6234
   Datum_Guyane_Francaise =	6235
   Datum_Hu_Tzu_Shan =	6236
   Datum_Hungarian_Datum_1972 =	6237
   Datum_Indonesian_Datum_1974 =	6238
   Datum_Indian_1954 =	6239
   Datum_Indian_1975 =	6240
   Datum_Jamaica_1875 =	6241
   Datum_Jamaica_1969 =	6242
   Datum_Kalianpur =	6243
   Datum_Kandawala =	6244
   Datum_Kertau =	6245
   Datum_Kuwait_Oil_Company =	6246
   Datum_La_Canoa =	6247
   Datum_Provisional_S_American_Datum_1956 =	6248
   Datum_Lake =	6249
   Datum_Leigon =	6250
   Datum_Liberia_1964 =	6251
   Datum_Lome =	6252
   Datum_Luzon_1911 =	6253
   Datum_Hito_XVIII_1963 =	6254
   Datum_Herat_North =	6255
   Datum_Mahe_1971 =	6256
   Datum_Makassar =	6257
   Datum_European_Reference_System_1989 =	6258
   Datum_Malongo_1987 =	6259
   Datum_Manoca =	6260
   Datum_Merchich =	6261
   Datum_Massawa =	6262
   Datum_Minna =	6263
   Datum_Mhast =	6264
   Datum_Monte_Mario =	6265
   Datum_M_poraloko =	6266
   Datum_North_American_Datum_1927 =	6267
   Datum_NAD_Michigan =	6268
   Datum_North_American_Datum_1983 =	6269
   Datum_Nahrwan_1967 =	6270
   Datum_Naparima_1972 =	6271
   Datum_New_Zealand_Geodetic_Datum_1949 =	6272
   Datum_NGO_1948 =	6273
   Datum_Datum_73 =	6274
   Datum_Nouvelle_Triangulation_Francaise =	6275
   Datum_NSWC_9Z_2 =	6276
   Datum_OSGB_1936 =	6277
   Datum_OSGB_1970_SN =	6278
   Datum_OS_SN_1980 =	6279
   Datum_Padang_1884 =	6280
   Datum_Palestine_1923 =	6281
   Datum_Pointe_Noire =	6282
   Datum_Geocentric_Datum_of_Australia_1994 =	6283
   Datum_Pulkovo_1942 =	6284
   Datum_Qatar =	6285
   Datum_Qatar_1948 =	6286
   Datum_Qornoq =	6287
   Datum_Loma_Quintana =	6288
   Datum_Amersfoort =	6289
   Datum_RT38 =	6290
   Datum_South_American_Datum_1969 =	6291
   Datum_Sapper_Hill_1943 =	6292
   Datum_Schwarzeck =	6293
   Datum_Segora =	6294
   Datum_Serindung =	6295
   Datum_Sudan =	6296
   Datum_Tananarive_1925 =	6297
   Datum_Timbalai_1948 =	6298
   Datum_TM65 =	6299
   Datum_TM75 =	6300
   Datum_Tokyo =	6301
   Datum_Trinidad_1903 =	6302
   Datum_Trucial_Coast_1948 =	6303
   Datum_Voirol_1875 =	6304
   Datum_Voirol_Unifie_1960 =	6305
   Datum_Bern_1938 =	6306
   Datum_Nord_Sahara_1959 =	6307
   Datum_Stockholm_1938 =	6308
   Datum_Yacare =	6309
   Datum_Yoff =	6310
   Datum_Zanderij =	6311
   Datum_Militar_Geographische_Institut =	6312
   Datum_Reseau_National_Belge_1972 =	6313
   Datum_Deutsche_Hauptdreiecksnetz =	6314
   Datum_Conakry_1905 =	6315
   Datum_WGS72 =	6322
   Datum_WGS72_Transit_Broadcast_Ephemeris =	6324
   Datum_WGS84 =	6326
   Datum_Ancienne_Triangulation_Francaise =	6901
   Datum_Nord_de_Guerre =	6902

Ellipsoid-Only Datum:

   Note: the numeric code is equal to the corresponding ellipsoid
   code, minus 1000.

   DatumE_Airy1830 =	6001
   DatumE_AiryModified1849 =	6002
   DatumE_AustralianNationalSpheroid =	6003
   DatumE_Bessel1841 =	6004
   DatumE_BesselModified =	6005
   DatumE_BesselNamibia =	6006
   DatumE_Clarke1858 =	6007
   DatumE_Clarke1866 =	6008
   DatumE_Clarke1866Michigan =	6009
   DatumE_Clarke1880_Benoit =	6010
   DatumE_Clarke1880_IGN =	6011
   DatumE_Clarke1880_RGS =	6012
   DatumE_Clarke1880_Arc =	6013
   DatumE_Clarke1880_SGA1922 =	6014
   DatumE_Everest1830_1937Adjustment =	6015
   DatumE_Everest1830_1967Definition =	6016
   DatumE_Everest1830_1975Definition =	6017
   DatumE_Everest1830Modified =	6018
   DatumE_GRS1980 =	6019
   DatumE_Helmert1906 =	6020
   DatumE_IndonesianNationalSpheroid =	6021
   DatumE_International1924 =	6022
   DatumE_International1967 =	6023
   DatumE_Krassowsky1960 =	6024
   DatumE_NWL9D =	6025
   DatumE_NWL10D =	6026
   DatumE_Plessis1817 =	6027
   DatumE_Struve1860 =	6028
   DatumE_WarOffice =	6029
   DatumE_WGS84 =	6030
   DatumE_GEM10C =	6031
   DatumE_OSU86F =	6032
   DatumE_OSU91A =	6033
   DatumE_Clarke1880 =	6034
   DatumE_Sphere =	6035

+----------------------------------+
6.3.2.3 Ellipsoid Codes

Ranges:

   0 = undefined
   [    1, 1000]  = Obsolete EPSG/POSC Ellipsoid codes
   [1001,  6999]  = Reserved by GeoTIFF
   [7000,  7999]  = EPSG Ellipsoid codes
   [8000, 32766]  = Reserved by GeoTIFF
   32767          = user-defined
   [32768, 65535] = Private User Implementations

Values:

   Ellipse_Airy_1830 =	7001
   Ellipse_Airy_Modified_1849 =	7002
   Ellipse_Australian_National_Spheroid =	7003
   Ellipse_Bessel_1841 =	7004
   Ellipse_Bessel_Modified =	7005
   Ellipse_Bessel_Namibia =	7006
   Ellipse_Clarke_1858 =	7007
   Ellipse_Clarke_1866 =	7008
   Ellipse_Clarke_1866_Michigan =	7009
   Ellipse_Clarke_1880_Benoit =	7010
   Ellipse_Clarke_1880_IGN =	7011
   Ellipse_Clarke_1880_RGS =	7012
   Ellipse_Clarke_1880_Arc =	7013
   Ellipse_Clarke_1880_SGA_1922 =	7014
   Ellipse_Everest_1830_1937_Adjustment =	7015
   Ellipse_Everest_1830_1967_Definition =	7016
   Ellipse_Everest_1830_1975_Definition =	7017
   Ellipse_Everest_1830_Modified =	7018
   Ellipse_GRS_1980 =	7019
   Ellipse_Helmert_1906 =	7020
   Ellipse_Indonesian_National_Spheroid =	7021
   Ellipse_International_1924 =	7022
   Ellipse_International_1967 =	7023
   Ellipse_Krassowsky_1940 =	7024
   Ellipse_NWL_9D =	7025
   Ellipse_NWL_10D =	7026
   Ellipse_Plessis_1817 =	7027
   Ellipse_Struve_1860 =	7028
   Ellipse_War_Office =	7029
   Ellipse_WGS_84 =	7030
   Ellipse_GEM_10C =	7031
   Ellipse_OSU86F =	7032
   Ellipse_OSU91A =	7033
   Ellipse_Clarke_1880 =	7034
   Ellipse_Sphere =	7035

+----------------------------------+
6.3.2.4 Prime Meridian Codes
Ranges:

   0 = undefined
   [    1,   100] = Obsolete EPSG/POSC Prime Meridian codes
   [  101,  7999] = Reserved by GeoTIFF
   [ 8000,  8999] = EPSG Prime Meridian Codes
   [ 9000, 32766] = Reserved by GeoTIFF
   32767          = user-defined
   [32768, 65535] = Private User Implementations

Values:

   PM_Greenwich =	8901
   PM_Lisbon =	8902
   PM_Paris =	8903
   PM_Bogota =	8904
   PM_Madrid =	8905
   PM_Rome =	8906
   PM_Bern =	8907
   PM_Jakarta =	8908
   PM_Ferro =	8909
   PM_Brussels =	8910
   PM_Stockholm =	8911

+----------------------------------+
6.3.3 Projected CS Codes
+----------------------------------+
6.3.3.1 Projected CS Type Codes
Ranges:

   [    1,   1000]  = Obsolete EPSG/POSC Projection System Codes
   [20000,  32760]  = EPSG Projection System codes
   32767            = user-defined
   [32768,  65535]  = Private User Implementations

Special Ranges:

1. For PCS utilising GeogCS with code in range 4201 through 4321 
(i.e. geodetic datum code 6201 through 6319): As far as is possible
 the PCS code will be of the format gggzz where ggg is (geodetic 
datum code -2000) and zz is zone.

2. For PCS utilising GeogCS with code out of range 4201 through 4321 
(i.e. geodetic datum code 6201 through 6319). PCS code 20xxx where 
xxx is a sequential number.

3. Other:
   WGS72 / UTM northern hemisphere:	322zz where zz is UTM zone number
   WGS72 / UTM southern hemisphere:	323zz where zz is UTM zone number
   WGS72BE / UTM northern hemisphere: 324zz where zz is UTM zone number
   WGS72BE / UTM southern hemisphere: 325zz where zz is UTM zone number
   WGS84 / UTM northern hemisphere:	326zz where zz is UTM zone number
   WGS84 / UTM southern hemisphere:	327zz where zz is UTM zone number
   US State Plane (NAD27):	267xx/320xx 
   US State Plane (NAD83):	269xx/321xx

Values:

   PCS_Adindan_UTM_zone_37N =	20137
   PCS_Adindan_UTM_zone_38N =	20138
   PCS_AGD66_AMG_zone_48 =	20248
   PCS_AGD66_AMG_zone_49 =	20249
   PCS_AGD66_AMG_zone_50 =	20250
   PCS_AGD66_AMG_zone_51 =	20251
   PCS_AGD66_AMG_zone_52 =	20252
   PCS_AGD66_AMG_zone_53 =	20253
   PCS_AGD66_AMG_zone_54 =	20254
   PCS_AGD66_AMG_zone_55 =	20255
   PCS_AGD66_AMG_zone_56 =	20256
   PCS_AGD66_AMG_zone_57 =	20257
   PCS_AGD66_AMG_zone_58 =	20258
   PCS_AGD84_AMG_zone_48 =	20348
   PCS_AGD84_AMG_zone_49 =	20349
   PCS_AGD84_AMG_zone_50 =	20350
   PCS_AGD84_AMG_zone_51 =	20351
   PCS_AGD84_AMG_zone_52 =	20352
   PCS_AGD84_AMG_zone_53 =	20353
   PCS_AGD84_AMG_zone_54 =	20354
   PCS_AGD84_AMG_zone_55 =	20355
   PCS_AGD84_AMG_zone_56 =	20356
   PCS_AGD84_AMG_zone_57 =	20357
   PCS_AGD84_AMG_zone_58 =	20358
   PCS_Ain_el_Abd_UTM_zone_37N =	20437
   PCS_Ain_el_Abd_UTM_zone_38N =	20438
   PCS_Ain_el_Abd_UTM_zone_39N =	20439
   PCS_Ain_el_Abd_Bahrain_Grid =	20499
   PCS_Afgooye_UTM_zone_38N =	20538
   PCS_Afgooye_UTM_zone_39N =	20539
   PCS_Lisbon_Portugese_Grid =	20700
   PCS_Aratu_UTM_zone_22S =	20822
   PCS_Aratu_UTM_zone_23S =	20823
   PCS_Aratu_UTM_zone_24S =	20824
   PCS_Arc_1950_Lo13 =	20973
   PCS_Arc_1950_Lo15 =	20975
   PCS_Arc_1950_Lo17 =	20977
   PCS_Arc_1950_Lo19 =	20979
   PCS_Arc_1950_Lo21 =	20981
   PCS_Arc_1950_Lo23 =	20983
   PCS_Arc_1950_Lo25 =	20985
   PCS_Arc_1950_Lo27 =	20987
   PCS_Arc_1950_Lo29 =	20989
   PCS_Arc_1950_Lo31 =	20991
   PCS_Arc_1950_Lo33 =	20993
   PCS_Arc_1950_Lo35 =	20995
   PCS_Batavia_NEIEZ =	21100
   PCS_Batavia_UTM_zone_48S =	21148
   PCS_Batavia_UTM_zone_49S =	21149
   PCS_Batavia_UTM_zone_50S =	21150
   PCS_Beijing_Gauss_zone_13 =	21413
   PCS_Beijing_Gauss_zone_14 =	21414
   PCS_Beijing_Gauss_zone_15 =	21415
   PCS_Beijing_Gauss_zone_16 =	21416
   PCS_Beijing_Gauss_zone_17 =	21417
   PCS_Beijing_Gauss_zone_18 =	21418
   PCS_Beijing_Gauss_zone_19 =	21419
   PCS_Beijing_Gauss_zone_20 =	21420
   PCS_Beijing_Gauss_zone_21 =	21421
   PCS_Beijing_Gauss_zone_22 =	21422
   PCS_Beijing_Gauss_zone_23 =	21423
   PCS_Beijing_Gauss_13N =	21473
   PCS_Beijing_Gauss_14N =	21474
   PCS_Beijing_Gauss_15N =	21475
   PCS_Beijing_Gauss_16N =	21476
   PCS_Beijing_Gauss_17N =	21477
   PCS_Beijing_Gauss_18N =	21478
   PCS_Beijing_Gauss_19N =	21479
   PCS_Beijing_Gauss_20N =	21480
   PCS_Beijing_Gauss_21N =	21481
   PCS_Beijing_Gauss_22N =	21482
   PCS_Beijing_Gauss_23N =	21483
   PCS_Belge_Lambert_50 =	21500
   PCS_Bern_1898_Swiss_Old =	21790
   PCS_Bogota_UTM_zone_17N =	21817
   PCS_Bogota_UTM_zone_18N =	21818
   PCS_Bogota_Colombia_3W =	21891
   PCS_Bogota_Colombia_Bogota =	21892
   PCS_Bogota_Colombia_3E =	21893
   PCS_Bogota_Colombia_6E =	21894
   PCS_Camacupa_UTM_32S =	22032
   PCS_Camacupa_UTM_33S =	22033
   PCS_C_Inchauspe_Argentina_1 =	22191
   PCS_C_Inchauspe_Argentina_2 =	22192
   PCS_C_Inchauspe_Argentina_3 =	22193
   PCS_C_Inchauspe_Argentina_4 =	22194
   PCS_C_Inchauspe_Argentina_5 =	22195
   PCS_C_Inchauspe_Argentina_6 =	22196
   PCS_C_Inchauspe_Argentina_7 =	22197
   PCS_Carthage_UTM_zone_32N =	22332
   PCS_Carthage_Nord_Tunisie =	22391
   PCS_Carthage_Sud_Tunisie =	22392
   PCS_Corrego_Alegre_UTM_23S =	22523
   PCS_Corrego_Alegre_UTM_24S =	22524
   PCS_Douala_UTM_zone_32N =	22832
   PCS_Egypt_1907_Red_Belt =	22992
   PCS_Egypt_1907_Purple_Belt =	22993
   PCS_Egypt_1907_Ext_Purple =	22994
   PCS_ED50_UTM_zone_28N =	23028
   PCS_ED50_UTM_zone_29N =	23029
   PCS_ED50_UTM_zone_30N =	23030
   PCS_ED50_UTM_zone_31N =	23031
   PCS_ED50_UTM_zone_32N =	23032
   PCS_ED50_UTM_zone_33N =	23033
   PCS_ED50_UTM_zone_34N =	23034
   PCS_ED50_UTM_zone_35N =	23035
   PCS_ED50_UTM_zone_36N =	23036
   PCS_ED50_UTM_zone_37N =	23037
   PCS_ED50_UTM_zone_38N =	23038
   PCS_Fahud_UTM_zone_39N =	23239
   PCS_Fahud_UTM_zone_40N =	23240
   PCS_Garoua_UTM_zone_33N =	23433
   PCS_ID74_UTM_zone_46N =	23846
   PCS_ID74_UTM_zone_47N =	23847
   PCS_ID74_UTM_zone_48N =	23848
   PCS_ID74_UTM_zone_49N =	23849
   PCS_ID74_UTM_zone_50N =	23850
   PCS_ID74_UTM_zone_51N =	23851
   PCS_ID74_UTM_zone_52N =	23852
   PCS_ID74_UTM_zone_53N =	23853
   PCS_ID74_UTM_zone_46S =	23886
   PCS_ID74_UTM_zone_47S =	23887
   PCS_ID74_UTM_zone_48S =	23888
   PCS_ID74_UTM_zone_49S =	23889
   PCS_ID74_UTM_zone_50S =	23890
   PCS_ID74_UTM_zone_51S =	23891
   PCS_ID74_UTM_zone_52S =	23892
   PCS_ID74_UTM_zone_53S =	23893
   PCS_ID74_UTM_zone_54S =	23894
   PCS_Indian_1954_UTM_47N =	23947
   PCS_Indian_1954_UTM_48N =	23948
   PCS_Indian_1975_UTM_47N =	24047
   PCS_Indian_1975_UTM_48N =	24048
   PCS_Jamaica_1875_Old_Grid =	24100
   PCS_JAD69_Jamaica_Grid =	24200
   PCS_Kalianpur_India_0 =	24370
   PCS_Kalianpur_India_I =	24371
   PCS_Kalianpur_India_IIa =	24372
   PCS_Kalianpur_India_IIIa =	24373
   PCS_Kalianpur_India_IVa =	24374
   PCS_Kalianpur_India_IIb =	24382
   PCS_Kalianpur_India_IIIb =	24383
   PCS_Kalianpur_India_IVb =	24384
   PCS_Kertau_Singapore_Grid =	24500
   PCS_Kertau_UTM_zone_47N =	24547
   PCS_Kertau_UTM_zone_48N =	24548
   PCS_La_Canoa_UTM_zone_20N =	24720
   PCS_La_Canoa_UTM_zone_21N =	24721
   PCS_PSAD56_UTM_zone_18N =	24818
   PCS_PSAD56_UTM_zone_19N =	24819
   PCS_PSAD56_UTM_zone_20N =	24820
   PCS_PSAD56_UTM_zone_21N =	24821
   PCS_PSAD56_UTM_zone_17S =	24877
   PCS_PSAD56_UTM_zone_18S =	24878
   PCS_PSAD56_UTM_zone_19S =	24879
   PCS_PSAD56_UTM_zone_20S =	24880
   PCS_PSAD56_Peru_west_zone =	24891
   PCS_PSAD56_Peru_central =	24892
   PCS_PSAD56_Peru_east_zone =	24893
   PCS_Leigon_Ghana_Grid =	25000
   PCS_Lome_UTM_zone_31N =	25231
   PCS_Luzon_Philippines_I =	25391
   PCS_Luzon_Philippines_II =	25392
   PCS_Luzon_Philippines_III =	25393
   PCS_Luzon_Philippines_IV =	25394
   PCS_Luzon_Philippines_V =	25395
   PCS_Makassar_NEIEZ =	25700
   PCS_Malongo_1987_UTM_32S =	25932
   PCS_Merchich_Nord_Maroc =	26191
   PCS_Merchich_Sud_Maroc =	26192
   PCS_Merchich_Sahara =	26193
   PCS_Massawa_UTM_zone_37N =	26237
   PCS_Minna_UTM_zone_31N =	26331
   PCS_Minna_UTM_zone_32N =	26332
   PCS_Minna_Nigeria_West =	26391
   PCS_Minna_Nigeria_Mid_Belt =	26392
   PCS_Minna_Nigeria_East =	26393
   PCS_Mhast_UTM_zone_32S =	26432
   PCS_Monte_Mario_Italy_1 =	26591
   PCS_Monte_Mario_Italy_2 =	26592
   PCS_M_poraloko_UTM_32N =	26632
   PCS_M_poraloko_UTM_32S =	26692
   PCS_NAD27_UTM_zone_3N =	26703
   PCS_NAD27_UTM_zone_4N =	26704
   PCS_NAD27_UTM_zone_5N =	26705
   PCS_NAD27_UTM_zone_6N =	26706
   PCS_NAD27_UTM_zone_7N =	26707
   PCS_NAD27_UTM_zone_8N =	26708
   PCS_NAD27_UTM_zone_9N =	26709
   PCS_NAD27_UTM_zone_10N =	26710
   PCS_NAD27_UTM_zone_11N =	26711
   PCS_NAD27_UTM_zone_12N =	26712
   PCS_NAD27_UTM_zone_13N =	26713
   PCS_NAD27_UTM_zone_14N =	26714
   PCS_NAD27_UTM_zone_15N =	26715
   PCS_NAD27_UTM_zone_16N =	26716
   PCS_NAD27_UTM_zone_17N =	26717
   PCS_NAD27_UTM_zone_18N =	26718
   PCS_NAD27_UTM_zone_19N =	26719
   PCS_NAD27_UTM_zone_20N =	26720
   PCS_NAD27_UTM_zone_21N =	26721
   PCS_NAD27_UTM_zone_22N =	26722
   PCS_NAD27_Alabama_East =	26729
   PCS_NAD27_Alabama_West =	26730
   PCS_NAD27_Alaska_zone_1 =	26731
   PCS_NAD27_Alaska_zone_2 =	26732
   PCS_NAD27_Alaska_zone_3 =	26733
   PCS_NAD27_Alaska_zone_4 =	26734
   PCS_NAD27_Alaska_zone_5 =	26735
   PCS_NAD27_Alaska_zone_6 =	26736
   PCS_NAD27_Alaska_zone_7 =	26737
   PCS_NAD27_Alaska_zone_8 =	26738
   PCS_NAD27_Alaska_zone_9 =	26739
   PCS_NAD27_Alaska_zone_10 =	26740
   PCS_NAD27_California_I =	26741
   PCS_NAD27_California_II =	26742
   PCS_NAD27_California_III =	26743
   PCS_NAD27_California_IV =	26744
   PCS_NAD27_California_V =	26745
   PCS_NAD27_California_VI =	26746
   PCS_NAD27_California_VII =	26747
   PCS_NAD27_Arizona_East =	26748
   PCS_NAD27_Arizona_Central =	26749
   PCS_NAD27_Arizona_West =	26750
   PCS_NAD27_Arkansas_North =	26751
   PCS_NAD27_Arkansas_South =	26752
   PCS_NAD27_Colorado_North =	26753
   PCS_NAD27_Colorado_Central =	26754
   PCS_NAD27_Colorado_South =	26755
   PCS_NAD27_Connecticut =	26756
   PCS_NAD27_Delaware =	26757
   PCS_NAD27_Florida_East =	26758
   PCS_NAD27_Florida_West =	26759
   PCS_NAD27_Florida_North =	26760
   PCS_NAD27_Hawaii_zone_1 =	26761
   PCS_NAD27_Hawaii_zone_2 =	26762
   PCS_NAD27_Hawaii_zone_3 =	26763
   PCS_NAD27_Hawaii_zone_4 =	26764
   PCS_NAD27_Hawaii_zone_5 =	26765
   PCS_NAD27_Georgia_East =	26766
   PCS_NAD27_Georgia_West =	26767
   PCS_NAD27_Idaho_East =	26768
   PCS_NAD27_Idaho_Central =	26769
   PCS_NAD27_Idaho_West =	26770
   PCS_NAD27_Illinois_East =	26771
   PCS_NAD27_Illinois_West =	26772
   PCS_NAD27_Indiana_East =	26773
   PCS_NAD27_BLM_14N_feet =	26774
   PCS_NAD27_Indiana_West =	26774
   PCS_NAD27_BLM_15N_feet =	26775
   PCS_NAD27_Iowa_North =	26775
   PCS_NAD27_BLM_16N_feet =	26776
   PCS_NAD27_Iowa_South =	26776
   PCS_NAD27_BLM_17N_feet =	26777
   PCS_NAD27_Kansas_North =	26777
   PCS_NAD27_Kansas_South =	26778
   PCS_NAD27_Kentucky_North =	26779
   PCS_NAD27_Kentucky_South =	26780
   PCS_NAD27_Louisiana_North =	26781
   PCS_NAD27_Louisiana_South =	26782
   PCS_NAD27_Maine_East =	26783
   PCS_NAD27_Maine_West =	26784
   PCS_NAD27_Maryland =	26785
   PCS_NAD27_Massachusetts =	26786
   PCS_NAD27_Massachusetts_Is =	26787
   PCS_NAD27_Michigan_North =	26788
   PCS_NAD27_Michigan_Central =	26789
   PCS_NAD27_Michigan_South =	26790
   PCS_NAD27_Minnesota_North =	26791
   PCS_NAD27_Minnesota_Cent =	26792
   PCS_NAD27_Minnesota_South =	26793
   PCS_NAD27_Mississippi_East =	26794
   PCS_NAD27_Mississippi_West =	26795
   PCS_NAD27_Missouri_East =	26796
   PCS_NAD27_Missouri_Central =	26797
   PCS_NAD27_Missouri_West =	26798
   PCS_NAD_Michigan_Michigan_East =	26801
   PCS_NAD_Michigan_Michigan_Old_Central =	26802
   PCS_NAD_Michigan_Michigan_West =	26803
   PCS_NAD83_UTM_zone_3N =	26903
   PCS_NAD83_UTM_zone_4N =	26904
   PCS_NAD83_UTM_zone_5N =	26905
   PCS_NAD83_UTM_zone_6N =	26906
   PCS_NAD83_UTM_zone_7N =	26907
   PCS_NAD83_UTM_zone_8N =	26908
   PCS_NAD83_UTM_zone_9N =	26909
   PCS_NAD83_UTM_zone_10N =	26910
   PCS_NAD83_UTM_zone_11N =	26911
   PCS_NAD83_UTM_zone_12N =	26912
   PCS_NAD83_UTM_zone_13N =	26913
   PCS_NAD83_UTM_zone_14N =	26914
   PCS_NAD83_UTM_zone_15N =	26915
   PCS_NAD83_UTM_zone_16N =	26916
   PCS_NAD83_UTM_zone_17N =	26917
   PCS_NAD83_UTM_zone_18N =	26918
   PCS_NAD83_UTM_zone_19N =	26919
   PCS_NAD83_UTM_zone_20N =	26920
   PCS_NAD83_UTM_zone_21N =	26921
   PCS_NAD83_UTM_zone_22N =	26922
   PCS_NAD83_UTM_zone_23N =	26923
   PCS_NAD83_Alabama_East =	26929
   PCS_NAD83_Alabama_West =	26930
   PCS_NAD83_Alaska_zone_1 =	26931
   PCS_NAD83_Alaska_zone_2 =	26932
   PCS_NAD83_Alaska_zone_3 =	26933
   PCS_NAD83_Alaska_zone_4 =	26934
   PCS_NAD83_Alaska_zone_5 =	26935
   PCS_NAD83_Alaska_zone_6 =	26936
   PCS_NAD83_Alaska_zone_7 =	26937
   PCS_NAD83_Alaska_zone_8 =	26938
   PCS_NAD83_Alaska_zone_9 =	26939
   PCS_NAD83_Alaska_zone_10 =	26940
   PCS_NAD83_California_1 =	26941
   PCS_NAD83_California_2 =	26942
   PCS_NAD83_California_3 =	26943
   PCS_NAD83_California_4 =	26944
   PCS_NAD83_California_5 =	26945
   PCS_NAD83_California_6 =	26946
   PCS_NAD83_Arizona_East =	26948
   PCS_NAD83_Arizona_Central =	26949
   PCS_NAD83_Arizona_West =	26950
   PCS_NAD83_Arkansas_North =	26951
   PCS_NAD83_Arkansas_South =	26952
   PCS_NAD83_Colorado_North =	26953
   PCS_NAD83_Colorado_Central =	26954
   PCS_NAD83_Colorado_South =	26955
   PCS_NAD83_Connecticut =	26956
   PCS_NAD83_Delaware =	26957
   PCS_NAD83_Florida_East =	26958
   PCS_NAD83_Florida_West =	26959
   PCS_NAD83_Florida_North =	26960
   PCS_NAD83_Hawaii_zone_1 =	26961
   PCS_NAD83_Hawaii_zone_2 =	26962
   PCS_NAD83_Hawaii_zone_3 =	26963
   PCS_NAD83_Hawaii_zone_4 =	26964
   PCS_NAD83_Hawaii_zone_5 =	26965
   PCS_NAD83_Georgia_East =	26966
   PCS_NAD83_Georgia_West =	26967
   PCS_NAD83_Idaho_East =	26968
   PCS_NAD83_Idaho_Central =	26969
   PCS_NAD83_Idaho_West =	26970
   PCS_NAD83_Illinois_East =	26971
   PCS_NAD83_Illinois_West =	26972
   PCS_NAD83_Indiana_East =	26973
   PCS_NAD83_Indiana_West =	26974
   PCS_NAD83_Iowa_North =	26975
   PCS_NAD83_Iowa_South =	26976
   PCS_NAD83_Kansas_North =	26977
   PCS_NAD83_Kansas_South =	26978
   PCS_NAD83_Kentucky_North =	26979
   PCS_NAD83_Kentucky_South =	26980
   PCS_NAD83_Louisiana_North =	26981
   PCS_NAD83_Louisiana_South =	26982
   PCS_NAD83_Maine_East =	26983
   PCS_NAD83_Maine_West =	26984
   PCS_NAD83_Maryland =	26985
   PCS_NAD83_Massachusetts =	26986
   PCS_NAD83_Massachusetts_Is =	26987
   PCS_NAD83_Michigan_North =	26988
   PCS_NAD83_Michigan_Central =	26989
   PCS_NAD83_Michigan_South =	26990
   PCS_NAD83_Minnesota_North =	26991
   PCS_NAD83_Minnesota_Cent =	26992
   PCS_NAD83_Minnesota_South =	26993
   PCS_NAD83_Mississippi_East =	26994
   PCS_NAD83_Mississippi_West =	26995
   PCS_NAD83_Missouri_East =	26996
   PCS_NAD83_Missouri_Central =	26997
   PCS_NAD83_Missouri_West =	26998
   PCS_Nahrwan_1967_UTM_38N =	27038
   PCS_Nahrwan_1967_UTM_39N =	27039
   PCS_Nahrwan_1967_UTM_40N =	27040
   PCS_Naparima_UTM_20N =	27120
   PCS_GD49_NZ_Map_Grid =	27200
   PCS_GD49_North_Island_Grid =	27291
   PCS_GD49_South_Island_Grid =	27292
   PCS_Datum_73_UTM_zone_29N =	27429
   PCS_ATF_Nord_de_Guerre =	27500
   PCS_NTF_France_I =	27581
   PCS_NTF_France_II =	27582
   PCS_NTF_France_III =	27583
   PCS_NTF_Nord_France =	27591
   PCS_NTF_Centre_France =	27592
   PCS_NTF_Sud_France =	27593
   PCS_British_National_Grid =	27700
   PCS_Point_Noire_UTM_32S =	28232
   PCS_GDA94_MGA_zone_48 =	28348
   PCS_GDA94_MGA_zone_49 =	28349
   PCS_GDA94_MGA_zone_50 =	28350
   PCS_GDA94_MGA_zone_51 =	28351
   PCS_GDA94_MGA_zone_52 =	28352
   PCS_GDA94_MGA_zone_53 =	28353
   PCS_GDA94_MGA_zone_54 =	28354
   PCS_GDA94_MGA_zone_55 =	28355
   PCS_GDA94_MGA_zone_56 =	28356
   PCS_GDA94_MGA_zone_57 =	28357
   PCS_GDA94_MGA_zone_58 =	28358
   PCS_Pulkovo_Gauss_zone_4 =	28404
   PCS_Pulkovo_Gauss_zone_5 =	28405
   PCS_Pulkovo_Gauss_zone_6 =	28406
   PCS_Pulkovo_Gauss_zone_7 =	28407
   PCS_Pulkovo_Gauss_zone_8 =	28408
   PCS_Pulkovo_Gauss_zone_9 =	28409
   PCS_Pulkovo_Gauss_zone_10 =	28410
   PCS_Pulkovo_Gauss_zone_11 =	28411
   PCS_Pulkovo_Gauss_zone_12 =	28412
   PCS_Pulkovo_Gauss_zone_13 =	28413
   PCS_Pulkovo_Gauss_zone_14 =	28414
   PCS_Pulkovo_Gauss_zone_15 =	28415
   PCS_Pulkovo_Gauss_zone_16 =	28416
   PCS_Pulkovo_Gauss_zone_17 =	28417
   PCS_Pulkovo_Gauss_zone_18 =	28418
   PCS_Pulkovo_Gauss_zone_19 =	28419
   PCS_Pulkovo_Gauss_zone_20 =	28420
   PCS_Pulkovo_Gauss_zone_21 =	28421
   PCS_Pulkovo_Gauss_zone_22 =	28422
   PCS_Pulkovo_Gauss_zone_23 =	28423
   PCS_Pulkovo_Gauss_zone_24 =	28424
   PCS_Pulkovo_Gauss_zone_25 =	28425
   PCS_Pulkovo_Gauss_zone_26 =	28426
   PCS_Pulkovo_Gauss_zone_27 =	28427
   PCS_Pulkovo_Gauss_zone_28 =	28428
   PCS_Pulkovo_Gauss_zone_29 =	28429
   PCS_Pulkovo_Gauss_zone_30 =	28430
   PCS_Pulkovo_Gauss_zone_31 =	28431
   PCS_Pulkovo_Gauss_zone_32 =	28432
   PCS_Pulkovo_Gauss_4N =	28464
   PCS_Pulkovo_Gauss_5N =	28465
   PCS_Pulkovo_Gauss_6N =	28466
   PCS_Pulkovo_Gauss_7N =	28467
   PCS_Pulkovo_Gauss_8N =	28468
   PCS_Pulkovo_Gauss_9N =	28469
   PCS_Pulkovo_Gauss_10N =	28470
   PCS_Pulkovo_Gauss_11N =	28471
   PCS_Pulkovo_Gauss_12N =	28472
   PCS_Pulkovo_Gauss_13N =	28473
   PCS_Pulkovo_Gauss_14N =	28474
   PCS_Pulkovo_Gauss_15N =	28475
   PCS_Pulkovo_Gauss_16N =	28476
   PCS_Pulkovo_Gauss_17N =	28477
   PCS_Pulkovo_Gauss_18N =	28478
   PCS_Pulkovo_Gauss_19N =	28479
   PCS_Pulkovo_Gauss_20N =	28480
   PCS_Pulkovo_Gauss_21N =	28481
   PCS_Pulkovo_Gauss_22N =	28482
   PCS_Pulkovo_Gauss_23N =	28483
   PCS_Pulkovo_Gauss_24N =	28484
   PCS_Pulkovo_Gauss_25N =	28485
   PCS_Pulkovo_Gauss_26N =	28486
   PCS_Pulkovo_Gauss_27N =	28487
   PCS_Pulkovo_Gauss_28N =	28488
   PCS_Pulkovo_Gauss_29N =	28489
   PCS_Pulkovo_Gauss_30N =	28490
   PCS_Pulkovo_Gauss_31N =	28491
   PCS_Pulkovo_Gauss_32N =	28492
   PCS_Qatar_National_Grid =	28600
   PCS_RD_Netherlands_Old =	28991
   PCS_RD_Netherlands_New =	28992
   PCS_SAD69_UTM_zone_18N =	29118
   PCS_SAD69_UTM_zone_19N =	29119
   PCS_SAD69_UTM_zone_20N =	29120
   PCS_SAD69_UTM_zone_21N =	29121
   PCS_SAD69_UTM_zone_22N =	29122
   PCS_SAD69_UTM_zone_17S =	29177
   PCS_SAD69_UTM_zone_18S =	29178
   PCS_SAD69_UTM_zone_19S =	29179
   PCS_SAD69_UTM_zone_20S =	29180
   PCS_SAD69_UTM_zone_21S =	29181
   PCS_SAD69_UTM_zone_22S =	29182
   PCS_SAD69_UTM_zone_23S =	29183
   PCS_SAD69_UTM_zone_24S =	29184
   PCS_SAD69_UTM_zone_25S =	29185
   PCS_Sapper_Hill_UTM_20S =	29220
   PCS_Sapper_Hill_UTM_21S =	29221
   PCS_Schwarzeck_UTM_33S =	29333
   PCS_Sudan_UTM_zone_35N =	29635
   PCS_Sudan_UTM_zone_36N =	29636
   PCS_Tananarive_Laborde =	29700
   PCS_Tananarive_UTM_38S =	29738
   PCS_Tananarive_UTM_39S =	29739
   PCS_Timbalai_1948_Borneo =	29800
   PCS_Timbalai_1948_UTM_49N =	29849
   PCS_Timbalai_1948_UTM_50N =	29850
   PCS_TM65_Irish_Nat_Grid =	29900
   PCS_Trinidad_1903_Trinidad =	30200
   PCS_TC_1948_UTM_zone_39N =	30339
   PCS_TC_1948_UTM_zone_40N =	30340
   PCS_Voirol_N_Algerie_ancien =	30491
   PCS_Voirol_S_Algerie_ancien =	30492
   PCS_Voirol_Unifie_N_Algerie =	30591
   PCS_Voirol_Unifie_S_Algerie =	30592
   PCS_Bern_1938_Swiss_New =	30600
   PCS_Nord_Sahara_UTM_29N =	30729
   PCS_Nord_Sahara_UTM_30N =	30730
   PCS_Nord_Sahara_UTM_31N =	30731
   PCS_Nord_Sahara_UTM_32N =	30732
   PCS_Yoff_UTM_zone_28N =	31028
   PCS_Zanderij_UTM_zone_21N =	31121
   PCS_MGI_Austria_West =	31291
   PCS_MGI_Austria_Central =	31292
   PCS_MGI_Austria_East =	31293
   PCS_Belge_Lambert_72 =	31300
   PCS_DHDN_Germany_zone_1 =	31491
   PCS_DHDN_Germany_zone_2 =	31492
   PCS_DHDN_Germany_zone_3 =	31493
   PCS_DHDN_Germany_zone_4 =	31494
   PCS_DHDN_Germany_zone_5 =	31495
   PCS_NAD27_Montana_North =	32001
   PCS_NAD27_Montana_Central =	32002
   PCS_NAD27_Montana_South =	32003
   PCS_NAD27_Nebraska_North =	32005
   PCS_NAD27_Nebraska_South =	32006
   PCS_NAD27_Nevada_East =	32007
   PCS_NAD27_Nevada_Central =	32008
   PCS_NAD27_Nevada_West =	32009
   PCS_NAD27_New_Hampshire =	32010
   PCS_NAD27_New_Jersey =	32011
   PCS_NAD27_New_Mexico_East =	32012
   PCS_NAD27_New_Mexico_Cent =	32013
   PCS_NAD27_New_Mexico_West =	32014
   PCS_NAD27_New_York_East =	32015
   PCS_NAD27_New_York_Central =	32016
   PCS_NAD27_New_York_West =	32017
   PCS_NAD27_New_York_Long_Is =	32018
   PCS_NAD27_North_Carolina =	32019
   PCS_NAD27_North_Dakota_N =	32020
   PCS_NAD27_North_Dakota_S =	32021
   PCS_NAD27_Ohio_North =	32022
   PCS_NAD27_Ohio_South =	32023
   PCS_NAD27_Oklahoma_North =	32024
   PCS_NAD27_Oklahoma_South =	32025
   PCS_NAD27_Oregon_North =	32026
   PCS_NAD27_Oregon_South =	32027
   PCS_NAD27_Pennsylvania_N =	32028
   PCS_NAD27_Pennsylvania_S =	32029
   PCS_NAD27_Rhode_Island =	32030
   PCS_NAD27_South_Carolina_N =	32031
   PCS_NAD27_South_Carolina_S =	32033
   PCS_NAD27_South_Dakota_N =	32034
   PCS_NAD27_South_Dakota_S =	32035
   PCS_NAD27_Tennessee =	32036
   PCS_NAD27_Texas_North =	32037
   PCS_NAD27_Texas_North_Cen =	32038
   PCS_NAD27_Texas_Central =	32039
   PCS_NAD27_Texas_South_Cen =	32040
   PCS_NAD27_Texas_South =	32041
   PCS_NAD27_Utah_North =	32042
   PCS_NAD27_Utah_Central =	32043
   PCS_NAD27_Utah_South =	32044
   PCS_NAD27_Vermont =	32045
   PCS_NAD27_Virginia_North =	32046
   PCS_NAD27_Virginia_South =	32047
   PCS_NAD27_Washington_North =	32048
   PCS_NAD27_Washington_South =	32049
   PCS_NAD27_West_Virginia_N =	32050
   PCS_NAD27_West_Virginia_S =	32051
   PCS_NAD27_Wisconsin_North =	32052
   PCS_NAD27_Wisconsin_Cen =	32053
   PCS_NAD27_Wisconsin_South =	32054
   PCS_NAD27_Wyoming_East =	32055
   PCS_NAD27_Wyoming_E_Cen =	32056
   PCS_NAD27_Wyoming_W_Cen =	32057
   PCS_NAD27_Wyoming_West =	32058
   PCS_NAD27_Puerto_Rico =	32059
   PCS_NAD27_St_Croix =	32060
   PCS_NAD83_Montana =	32100
   PCS_NAD83_Nebraska =	32104
   PCS_NAD83_Nevada_East =	32107
   PCS_NAD83_Nevada_Central =	32108
   PCS_NAD83_Nevada_West =	32109
   PCS_NAD83_New_Hampshire =	32110
   PCS_NAD83_New_Jersey =	32111
   PCS_NAD83_New_Mexico_East =	32112
   PCS_NAD83_New_Mexico_Cent =	32113
   PCS_NAD83_New_Mexico_West =	32114
   PCS_NAD83_New_York_East =	32115
   PCS_NAD83_New_York_Central =	32116
   PCS_NAD83_New_York_West =	32117
   PCS_NAD83_New_York_Long_Is =	32118
   PCS_NAD83_North_Carolina =	32119
   PCS_NAD83_North_Dakota_N =	32120
   PCS_NAD83_North_Dakota_S =	32121
   PCS_NAD83_Ohio_North =	32122
   PCS_NAD83_Ohio_South =	32123
   PCS_NAD83_Oklahoma_North =	32124
   PCS_NAD83_Oklahoma_South =	32125
   PCS_NAD83_Oregon_North =	32126
   PCS_NAD83_Oregon_South =	32127
   PCS_NAD83_Pennsylvania_N =	32128
   PCS_NAD83_Pennsylvania_S =	32129
   PCS_NAD83_Rhode_Island =	32130
   PCS_NAD83_South_Carolina =	32133
   PCS_NAD83_South_Dakota_N =	32134
   PCS_NAD83_South_Dakota_S =	32135
   PCS_NAD83_Tennessee =	32136
   PCS_NAD83_Texas_North =	32137
   PCS_NAD83_Texas_North_Cen =	32138
   PCS_NAD83_Texas_Central =	32139
   PCS_NAD83_Texas_South_Cen =	32140
   PCS_NAD83_Texas_South =	32141
   PCS_NAD83_Utah_North =	32142
   PCS_NAD83_Utah_Central =	32143
   PCS_NAD83_Utah_South =	32144
   PCS_NAD83_Vermont =	32145
   PCS_NAD83_Virginia_North =	32146
   PCS_NAD83_Virginia_South =	32147
   PCS_NAD83_Washington_North =	32148
   PCS_NAD83_Washington_South =	32149
   PCS_NAD83_West_Virginia_N =	32150
   PCS_NAD83_West_Virginia_S =	32151
   PCS_NAD83_Wisconsin_North =	32152
   PCS_NAD83_Wisconsin_Cen =	32153
   PCS_NAD83_Wisconsin_South =	32154
   PCS_NAD83_Wyoming_East =	32155
   PCS_NAD83_Wyoming_E_Cen =	32156
   PCS_NAD83_Wyoming_W_Cen =	32157
   PCS_NAD83_Wyoming_West =	32158
   PCS_NAD83_Puerto_Rico_Virgin_Is =	32161
   PCS_WGS72_UTM_zone_1N =	32201
   PCS_WGS72_UTM_zone_2N =	32202
   PCS_WGS72_UTM_zone_3N =	32203
   PCS_WGS72_UTM_zone_4N =	32204
   PCS_WGS72_UTM_zone_5N =	32205
   PCS_WGS72_UTM_zone_6N =	32206
   PCS_WGS72_UTM_zone_7N =	32207
   PCS_WGS72_UTM_zone_8N =	32208
   PCS_WGS72_UTM_zone_9N =	32209
   PCS_WGS72_UTM_zone_10N =	32210
   PCS_WGS72_UTM_zone_11N =	32211
   PCS_WGS72_UTM_zone_12N =	32212
   PCS_WGS72_UTM_zone_13N =	32213
   PCS_WGS72_UTM_zone_14N =	32214
   PCS_WGS72_UTM_zone_15N =	32215
   PCS_WGS72_UTM_zone_16N =	32216
   PCS_WGS72_UTM_zone_17N =	32217
   PCS_WGS72_UTM_zone_18N =	32218
   PCS_WGS72_UTM_zone_19N =	32219
   PCS_WGS72_UTM_zone_20N =	32220
   PCS_WGS72_UTM_zone_21N =	32221
   PCS_WGS72_UTM_zone_22N =	32222
   PCS_WGS72_UTM_zone_23N =	32223
   PCS_WGS72_UTM_zone_24N =	32224
   PCS_WGS72_UTM_zone_25N =	32225
   PCS_WGS72_UTM_zone_26N =	32226
   PCS_WGS72_UTM_zone_27N =	32227
   PCS_WGS72_UTM_zone_28N =	32228
   PCS_WGS72_UTM_zone_29N =	32229
   PCS_WGS72_UTM_zone_30N =	32230
   PCS_WGS72_UTM_zone_31N =	32231
   PCS_WGS72_UTM_zone_32N =	32232
   PCS_WGS72_UTM_zone_33N =	32233
   PCS_WGS72_UTM_zone_34N =	32234
   PCS_WGS72_UTM_zone_35N =	32235
   PCS_WGS72_UTM_zone_36N =	32236
   PCS_WGS72_UTM_zone_37N =	32237
   PCS_WGS72_UTM_zone_38N =	32238
   PCS_WGS72_UTM_zone_39N =	32239
   PCS_WGS72_UTM_zone_40N =	32240
   PCS_WGS72_UTM_zone_41N =	32241
   PCS_WGS72_UTM_zone_42N =	32242
   PCS_WGS72_UTM_zone_43N =	32243
   PCS_WGS72_UTM_zone_44N =	32244
   PCS_WGS72_UTM_zone_45N =	32245
   PCS_WGS72_UTM_zone_46N =	32246
   PCS_WGS72_UTM_zone_47N =	32247
   PCS_WGS72_UTM_zone_48N =	32248
   PCS_WGS72_UTM_zone_49N =	32249
   PCS_WGS72_UTM_zone_50N =	32250
   PCS_WGS72_UTM_zone_51N =	32251
   PCS_WGS72_UTM_zone_52N =	32252
   PCS_WGS72_UTM_zone_53N =	32253
   PCS_WGS72_UTM_zone_54N =	32254
   PCS_WGS72_UTM_zone_55N =	32255
   PCS_WGS72_UTM_zone_56N =	32256
   PCS_WGS72_UTM_zone_57N =	32257
   PCS_WGS72_UTM_zone_58N =	32258
   PCS_WGS72_UTM_zone_59N =	32259
   PCS_WGS72_UTM_zone_60N =	32260
   PCS_WGS72_UTM_zone_1S =	32301
   PCS_WGS72_UTM_zone_2S =	32302
   PCS_WGS72_UTM_zone_3S =	32303
   PCS_WGS72_UTM_zone_4S =	32304
   PCS_WGS72_UTM_zone_5S =	32305
   PCS_WGS72_UTM_zone_6S =	32306
   PCS_WGS72_UTM_zone_7S =	32307
   PCS_WGS72_UTM_zone_8S =	32308
   PCS_WGS72_UTM_zone_9S =	32309
   PCS_WGS72_UTM_zone_10S =	32310
   PCS_WGS72_UTM_zone_11S =	32311
   PCS_WGS72_UTM_zone_12S =	32312
   PCS_WGS72_UTM_zone_13S =	32313
   PCS_WGS72_UTM_zone_14S =	32314
   PCS_WGS72_UTM_zone_15S =	32315
   PCS_WGS72_UTM_zone_16S =	32316
   PCS_WGS72_UTM_zone_17S =	32317
   PCS_WGS72_UTM_zone_18S =	32318
   PCS_WGS72_UTM_zone_19S =	32319
   PCS_WGS72_UTM_zone_20S =	32320
   PCS_WGS72_UTM_zone_21S =	32321
   PCS_WGS72_UTM_zone_22S =	32322
   PCS_WGS72_UTM_zone_23S =	32323
   PCS_WGS72_UTM_zone_24S =	32324
   PCS_WGS72_UTM_zone_25S =	32325
   PCS_WGS72_UTM_zone_26S =	32326
   PCS_WGS72_UTM_zone_27S =	32327
   PCS_WGS72_UTM_zone_28S =	32328
   PCS_WGS72_UTM_zone_29S =	32329
   PCS_WGS72_UTM_zone_30S =	32330
   PCS_WGS72_UTM_zone_31S =	32331
   PCS_WGS72_UTM_zone_32S =	32332
   PCS_WGS72_UTM_zone_33S =	32333
   PCS_WGS72_UTM_zone_34S =	32334
   PCS_WGS72_UTM_zone_35S =	32335
   PCS_WGS72_UTM_zone_36S =	32336
   PCS_WGS72_UTM_zone_37S =	32337
   PCS_WGS72_UTM_zone_38S =	32338
   PCS_WGS72_UTM_zone_39S =	32339
   PCS_WGS72_UTM_zone_40S =	32340
   PCS_WGS72_UTM_zone_41S =	32341
   PCS_WGS72_UTM_zone_42S =	32342
   PCS_WGS72_UTM_zone_43S =	32343
   PCS_WGS72_UTM_zone_44S =	32344
   PCS_WGS72_UTM_zone_45S =	32345
   PCS_WGS72_UTM_zone_46S =	32346
   PCS_WGS72_UTM_zone_47S =	32347
   PCS_WGS72_UTM_zone_48S =	32348
   PCS_WGS72_UTM_zone_49S =	32349
   PCS_WGS72_UTM_zone_50S =	32350
   PCS_WGS72_UTM_zone_51S =	32351
   PCS_WGS72_UTM_zone_52S =	32352
   PCS_WGS72_UTM_zone_53S =	32353
   PCS_WGS72_UTM_zone_54S =	32354
   PCS_WGS72_UTM_zone_55S =	32355
   PCS_WGS72_UTM_zone_56S =	32356
   PCS_WGS72_UTM_zone_57S =	32357
   PCS_WGS72_UTM_zone_58S =	32358
   PCS_WGS72_UTM_zone_59S =	32359
   PCS_WGS72_UTM_zone_60S =	32360
   PCS_WGS72BE_UTM_zone_1N =	32401
   PCS_WGS72BE_UTM_zone_2N =	32402
   PCS_WGS72BE_UTM_zone_3N =	32403
   PCS_WGS72BE_UTM_zone_4N =	32404
   PCS_WGS72BE_UTM_zone_5N =	32405
   PCS_WGS72BE_UTM_zone_6N =	32406
   PCS_WGS72BE_UTM_zone_7N =	32407
   PCS_WGS72BE_UTM_zone_8N =	32408
   PCS_WGS72BE_UTM_zone_9N =	32409
   PCS_WGS72BE_UTM_zone_10N =	32410
   PCS_WGS72BE_UTM_zone_11N =	32411
   PCS_WGS72BE_UTM_zone_12N =	32412
   PCS_WGS72BE_UTM_zone_13N =	32413
   PCS_WGS72BE_UTM_zone_14N =	32414
   PCS_WGS72BE_UTM_zone_15N =	32415
   PCS_WGS72BE_UTM_zone_16N =	32416
   PCS_WGS72BE_UTM_zone_17N =	32417
   PCS_WGS72BE_UTM_zone_18N =	32418
   PCS_WGS72BE_UTM_zone_19N =	32419
   PCS_WGS72BE_UTM_zone_20N =	32420
   PCS_WGS72BE_UTM_zone_21N =	32421
   PCS_WGS72BE_UTM_zone_22N =	32422
   PCS_WGS72BE_UTM_zone_23N =	32423
   PCS_WGS72BE_UTM_zone_24N =	32424
   PCS_WGS72BE_UTM_zone_25N =	32425
   PCS_WGS72BE_UTM_zone_26N =	32426
   PCS_WGS72BE_UTM_zone_27N =	32427
   PCS_WGS72BE_UTM_zone_28N =	32428
   PCS_WGS72BE_UTM_zone_29N =	32429
   PCS_WGS72BE_UTM_zone_30N =	32430
   PCS_WGS72BE_UTM_zone_31N =	32431
   PCS_WGS72BE_UTM_zone_32N =	32432
   PCS_WGS72BE_UTM_zone_33N =	32433
   PCS_WGS72BE_UTM_zone_34N =	32434
   PCS_WGS72BE_UTM_zone_35N =	32435
   PCS_WGS72BE_UTM_zone_36N =	32436
   PCS_WGS72BE_UTM_zone_37N =	32437
   PCS_WGS72BE_UTM_zone_38N =	32438
   PCS_WGS72BE_UTM_zone_39N =	32439
   PCS_WGS72BE_UTM_zone_40N =	32440
   PCS_WGS72BE_UTM_zone_41N =	32441
   PCS_WGS72BE_UTM_zone_42N =	32442
   PCS_WGS72BE_UTM_zone_43N =	32443
   PCS_WGS72BE_UTM_zone_44N =	32444
   PCS_WGS72BE_UTM_zone_45N =	32445
   PCS_WGS72BE_UTM_zone_46N =	32446
   PCS_WGS72BE_UTM_zone_47N =	32447
   PCS_WGS72BE_UTM_zone_48N =	32448
   PCS_WGS72BE_UTM_zone_49N =	32449
   PCS_WGS72BE_UTM_zone_50N =	32450
   PCS_WGS72BE_UTM_zone_51N =	32451
   PCS_WGS72BE_UTM_zone_52N =	32452
   PCS_WGS72BE_UTM_zone_53N =	32453
   PCS_WGS72BE_UTM_zone_54N =	32454
   PCS_WGS72BE_UTM_zone_55N =	32455
   PCS_WGS72BE_UTM_zone_56N =	32456
   PCS_WGS72BE_UTM_zone_57N =	32457
   PCS_WGS72BE_UTM_zone_58N =	32458
   PCS_WGS72BE_UTM_zone_59N =	32459
   PCS_WGS72BE_UTM_zone_60N =	32460
   PCS_WGS72BE_UTM_zone_1S =	32501
   PCS_WGS72BE_UTM_zone_2S =	32502
   PCS_WGS72BE_UTM_zone_3S =	32503
   PCS_WGS72BE_UTM_zone_4S =	32504
   PCS_WGS72BE_UTM_zone_5S =	32505
   PCS_WGS72BE_UTM_zone_6S =	32506
   PCS_WGS72BE_UTM_zone_7S =	32507
   PCS_WGS72BE_UTM_zone_8S =	32508
   PCS_WGS72BE_UTM_zone_9S =	32509
   PCS_WGS72BE_UTM_zone_10S =	32510
   PCS_WGS72BE_UTM_zone_11S =	32511
   PCS_WGS72BE_UTM_zone_12S =	32512
   PCS_WGS72BE_UTM_zone_13S =	32513
   PCS_WGS72BE_UTM_zone_14S =	32514
   PCS_WGS72BE_UTM_zone_15S =	32515
   PCS_WGS72BE_UTM_zone_16S =	32516
   PCS_WGS72BE_UTM_zone_17S =	32517
   PCS_WGS72BE_UTM_zone_18S =	32518
   PCS_WGS72BE_UTM_zone_19S =	32519
   PCS_WGS72BE_UTM_zone_20S =	32520
   PCS_WGS72BE_UTM_zone_21S =	32521
   PCS_WGS72BE_UTM_zone_22S =	32522
   PCS_WGS72BE_UTM_zone_23S =	32523
   PCS_WGS72BE_UTM_zone_24S =	32524
   PCS_WGS72BE_UTM_zone_25S =	32525
   PCS_WGS72BE_UTM_zone_26S =	32526
   PCS_WGS72BE_UTM_zone_27S =	32527
   PCS_WGS72BE_UTM_zone_28S =	32528
   PCS_WGS72BE_UTM_zone_29S =	32529
   PCS_WGS72BE_UTM_zone_30S =	32530
   PCS_WGS72BE_UTM_zone_31S =	32531
   PCS_WGS72BE_UTM_zone_32S =	32532
   PCS_WGS72BE_UTM_zone_33S =	32533
   PCS_WGS72BE_UTM_zone_34S =	32534
   PCS_WGS72BE_UTM_zone_35S =	32535
   PCS_WGS72BE_UTM_zone_36S =	32536
   PCS_WGS72BE_UTM_zone_37S =	32537
   PCS_WGS72BE_UTM_zone_38S =	32538
   PCS_WGS72BE_UTM_zone_39S =	32539
   PCS_WGS72BE_UTM_zone_40S =	32540
   PCS_WGS72BE_UTM_zone_41S =	32541
   PCS_WGS72BE_UTM_zone_42S =	32542
   PCS_WGS72BE_UTM_zone_43S =	32543
   PCS_WGS72BE_UTM_zone_44S =	32544
   PCS_WGS72BE_UTM_zone_45S =	32545
   PCS_WGS72BE_UTM_zone_46S =	32546
   PCS_WGS72BE_UTM_zone_47S =	32547
   PCS_WGS72BE_UTM_zone_48S =	32548
   PCS_WGS72BE_UTM_zone_49S =	32549
   PCS_WGS72BE_UTM_zone_50S =	32550
   PCS_WGS72BE_UTM_zone_51S =	32551
   PCS_WGS72BE_UTM_zone_52S =	32552
   PCS_WGS72BE_UTM_zone_53S =	32553
   PCS_WGS72BE_UTM_zone_54S =	32554
   PCS_WGS72BE_UTM_zone_55S =	32555
   PCS_WGS72BE_UTM_zone_56S =	32556
   PCS_WGS72BE_UTM_zone_57S =	32557
   PCS_WGS72BE_UTM_zone_58S =	32558
   PCS_WGS72BE_UTM_zone_59S =	32559
   PCS_WGS72BE_UTM_zone_60S =	32560
   PCS_WGS84_UTM_zone_1N =	32601
   PCS_WGS84_UTM_zone_2N =	32602
   PCS_WGS84_UTM_zone_3N =	32603
   PCS_WGS84_UTM_zone_4N =	32604
   PCS_WGS84_UTM_zone_5N =	32605
   PCS_WGS84_UTM_zone_6N =	32606
   PCS_WGS84_UTM_zone_7N =	32607
   PCS_WGS84_UTM_zone_8N =	32608
   PCS_WGS84_UTM_zone_9N =	32609
   PCS_WGS84_UTM_zone_10N =	32610
   PCS_WGS84_UTM_zone_11N =	32611
   PCS_WGS84_UTM_zone_12N =	32612
   PCS_WGS84_UTM_zone_13N =	32613
   PCS_WGS84_UTM_zone_14N =	32614
   PCS_WGS84_UTM_zone_15N =	32615
   PCS_WGS84_UTM_zone_16N =	32616
   PCS_WGS84_UTM_zone_17N =	32617
   PCS_WGS84_UTM_zone_18N =	32618
   PCS_WGS84_UTM_zone_19N =	32619
   PCS_WGS84_UTM_zone_20N =	32620
   PCS_WGS84_UTM_zone_21N =	32621
   PCS_WGS84_UTM_zone_22N =	32622
   PCS_WGS84_UTM_zone_23N =	32623
   PCS_WGS84_UTM_zone_24N =	32624
   PCS_WGS84_UTM_zone_25N =	32625
   PCS_WGS84_UTM_zone_26N =	32626
   PCS_WGS84_UTM_zone_27N =	32627
   PCS_WGS84_UTM_zone_28N =	32628
   PCS_WGS84_UTM_zone_29N =	32629
   PCS_WGS84_UTM_zone_30N =	32630
   PCS_WGS84_UTM_zone_31N =	32631
   PCS_WGS84_UTM_zone_32N =	32632
   PCS_WGS84_UTM_zone_33N =	32633
   PCS_WGS84_UTM_zone_34N =	32634
   PCS_WGS84_UTM_zone_35N =	32635
   PCS_WGS84_UTM_zone_36N =	32636
   PCS_WGS84_UTM_zone_37N =	32637
   PCS_WGS84_UTM_zone_38N =	32638
   PCS_WGS84_UTM_zone_39N =	32639
   PCS_WGS84_UTM_zone_40N =	32640
   PCS_WGS84_UTM_zone_41N =	32641
   PCS_WGS84_UTM_zone_42N =	32642
   PCS_WGS84_UTM_zone_43N =	32643
   PCS_WGS84_UTM_zone_44N =	32644
   PCS_WGS84_UTM_zone_45N =	32645
   PCS_WGS84_UTM_zone_46N =	32646
   PCS_WGS84_UTM_zone_47N =	32647
   PCS_WGS84_UTM_zone_48N =	32648
   PCS_WGS84_UTM_zone_49N =	32649
   PCS_WGS84_UTM_zone_50N =	32650
   PCS_WGS84_UTM_zone_51N =	32651
   PCS_WGS84_UTM_zone_52N =	32652
   PCS_WGS84_UTM_zone_53N =	32653
   PCS_WGS84_UTM_zone_54N =	32654
   PCS_WGS84_UTM_zone_55N =	32655
   PCS_WGS84_UTM_zone_56N =	32656
   PCS_WGS84_UTM_zone_57N =	32657
   PCS_WGS84_UTM_zone_58N =	32658
   PCS_WGS84_UTM_zone_59N =	32659
   PCS_WGS84_UTM_zone_60N =	32660
   PCS_WGS84_UTM_zone_1S =	32701
   PCS_WGS84_UTM_zone_2S =	32702
   PCS_WGS84_UTM_zone_3S =	32703
   PCS_WGS84_UTM_zone_4S =	32704
   PCS_WGS84_UTM_zone_5S =	32705
   PCS_WGS84_UTM_zone_6S =	32706
   PCS_WGS84_UTM_zone_7S =	32707
   PCS_WGS84_UTM_zone_8S =	32708
   PCS_WGS84_UTM_zone_9S =	32709
   PCS_WGS84_UTM_zone_10S =	32710
   PCS_WGS84_UTM_zone_11S =	32711
   PCS_WGS84_UTM_zone_12S =	32712
   PCS_WGS84_UTM_zone_13S =	32713
   PCS_WGS84_UTM_zone_14S =	32714
   PCS_WGS84_UTM_zone_15S =	32715
   PCS_WGS84_UTM_zone_16S =	32716
   PCS_WGS84_UTM_zone_17S =	32717
   PCS_WGS84_UTM_zone_18S =	32718
   PCS_WGS84_UTM_zone_19S =	32719
   PCS_WGS84_UTM_zone_20S =	32720
   PCS_WGS84_UTM_zone_21S =	32721
   PCS_WGS84_UTM_zone_22S =	32722
   PCS_WGS84_UTM_zone_23S =	32723
   PCS_WGS84_UTM_zone_24S =	32724
   PCS_WGS84_UTM_zone_25S =	32725
   PCS_WGS84_UTM_zone_26S =	32726
   PCS_WGS84_UTM_zone_27S =	32727
   PCS_WGS84_UTM_zone_28S =	32728
   PCS_WGS84_UTM_zone_29S =	32729
   PCS_WGS84_UTM_zone_30S =	32730
   PCS_WGS84_UTM_zone_31S =	32731
   PCS_WGS84_UTM_zone_32S =	32732
   PCS_WGS84_UTM_zone_33S =	32733
   PCS_WGS84_UTM_zone_34S =	32734
   PCS_WGS84_UTM_zone_35S =	32735
   PCS_WGS84_UTM_zone_36S =	32736
   PCS_WGS84_UTM_zone_37S =	32737
   PCS_WGS84_UTM_zone_38S =	32738
   PCS_WGS84_UTM_zone_39S =	32739
   PCS_WGS84_UTM_zone_40S =	32740
   PCS_WGS84_UTM_zone_41S =	32741
   PCS_WGS84_UTM_zone_42S =	32742
   PCS_WGS84_UTM_zone_43S =	32743
   PCS_WGS84_UTM_zone_44S =	32744
   PCS_WGS84_UTM_zone_45S =	32745
   PCS_WGS84_UTM_zone_46S =	32746
   PCS_WGS84_UTM_zone_47S =	32747
   PCS_WGS84_UTM_zone_48S =	32748
   PCS_WGS84_UTM_zone_49S =	32749
   PCS_WGS84_UTM_zone_50S =	32750
   PCS_WGS84_UTM_zone_51S =	32751
   PCS_WGS84_UTM_zone_52S =	32752
   PCS_WGS84_UTM_zone_53S =	32753
   PCS_WGS84_UTM_zone_54S =	32754
   PCS_WGS84_UTM_zone_55S =	32755
   PCS_WGS84_UTM_zone_56S =	32756
   PCS_WGS84_UTM_zone_57S =	32757
   PCS_WGS84_UTM_zone_58S =	32758
   PCS_WGS84_UTM_zone_59S =	32759
   PCS_WGS84_UTM_zone_60S =	32760

+----------------------------------+
6.3.3.2 Projection Codes
Note: Projections do not include GCS or PCS definitions. If possible, use the PCS code for standard projected coordinate systems, and use this code only if nonstandard datums are required.

Ranges:

   0 = undefined
   [    1,  9999] = Obsolete EPSG/POSC Projection codes
   [10000, 19999] = EPSG/POSC Projection codes
   32767          = user-defined
   [32768, 65535] = Private User Implementations

Special Ranges:

  US State Plane Format:    1sszz
          where ss is USC&GS State code
          zz is USC&GS zone code for NAD27 zones
          zz is (USC&GS zone code + 30) for NAD83 zones

  Larger zoned systems (16000-17999)	
   UTM (North)	Format:  160zz	
   UTM (South)	Format:  161zz		
   zoned Universal Gauss-Kruger	Format:  162zz	
   Universal Gauss-Kruger (unzoned)	Format:  163zz
   Australian Map Grid	Format:  174zz	
   Southern African STM	Format:  175zz	

  Smaller zoned systems:	Format:  18ssz
	     where ss is sequential system number	
	     z is zone code					
						
  Single zone projections	Format:   199ss
	     where ss is sequential system number	

Values:

   Proj_Alabama_CS27_East =	10101
   Proj_Alabama_CS27_West =	10102
   Proj_Alabama_CS83_East =	10131
   Proj_Alabama_CS83_West =	10132
   Proj_Arizona_Coordinate_System_east =	10201
   Proj_Arizona_Coordinate_System_Central =	10202
   Proj_Arizona_Coordinate_System_west =	10203
   Proj_Arizona_CS83_east =	10231
   Proj_Arizona_CS83_Central =	10232
   Proj_Arizona_CS83_west =	10233
   Proj_Arkansas_CS27_North =	10301
   Proj_Arkansas_CS27_South =	10302
   Proj_Arkansas_CS83_North =	10331
   Proj_Arkansas_CS83_South =	10332
   Proj_California_CS27_I =	10401
   Proj_California_CS27_II =	10402
   Proj_California_CS27_III =	10403
   Proj_California_CS27_IV =	10404
   Proj_California_CS27_V =	10405
   Proj_California_CS27_VI =	10406
   Proj_California_CS27_VII =	10407
   Proj_California_CS83_1 =	10431
   Proj_California_CS83_2 =	10432
   Proj_California_CS83_3 =	10433
   Proj_California_CS83_4 =	10434
   Proj_California_CS83_5 =	10435
   Proj_California_CS83_6 =	10436
   Proj_Colorado_CS27_North =	10501
   Proj_Colorado_CS27_Central =	10502
   Proj_Colorado_CS27_South =	10503
   Proj_Colorado_CS83_North =	10531
   Proj_Colorado_CS83_Central =	10532
   Proj_Colorado_CS83_South =	10533
   Proj_Connecticut_CS27 =	10600
   Proj_Connecticut_CS83 =	10630
   Proj_Delaware_CS27 =	10700
   Proj_Delaware_CS83 =	10730
   Proj_Florida_CS27_East =	10901
   Proj_Florida_CS27_West =	10902
   Proj_Florida_CS27_North =	10903
   Proj_Florida_CS83_East =	10931
   Proj_Florida_CS83_West =	10932
   Proj_Florida_CS83_North =	10933
   Proj_Georgia_CS27_East =	11001
   Proj_Georgia_CS27_West =	11002
   Proj_Georgia_CS83_East =	11031
   Proj_Georgia_CS83_West =	11032
   Proj_Idaho_CS27_East =	11101
   Proj_Idaho_CS27_Central =	11102
   Proj_Idaho_CS27_West =	11103
   Proj_Idaho_CS83_East =	11131
   Proj_Idaho_CS83_Central =	11132
   Proj_Idaho_CS83_West =	11133
   Proj_Illinois_CS27_East =	11201
   Proj_Illinois_CS27_West =	11202
   Proj_Illinois_CS83_East =	11231
   Proj_Illinois_CS83_West =	11232
   Proj_Indiana_CS27_East =	11301
   Proj_Indiana_CS27_West =	11302
   Proj_Indiana_CS83_East =	11331
   Proj_Indiana_CS83_West =	11332
   Proj_Iowa_CS27_North =	11401
   Proj_Iowa_CS27_South =	11402
   Proj_Iowa_CS83_North =	11431
   Proj_Iowa_CS83_South =	11432
   Proj_Kansas_CS27_North =	11501
   Proj_Kansas_CS27_South =	11502
   Proj_Kansas_CS83_North =	11531
   Proj_Kansas_CS83_South =	11532
   Proj_Kentucky_CS27_North =	11601
   Proj_Kentucky_CS27_South =	11602
   Proj_Kentucky_CS83_North =	11631
   Proj_Kentucky_CS83_South =	11632
   Proj_Louisiana_CS27_North =	11701
   Proj_Louisiana_CS27_South =	11702
   Proj_Louisiana_CS83_North =	11731
   Proj_Louisiana_CS83_South =	11732
   Proj_Maine_CS27_East =	11801
   Proj_Maine_CS27_West =	11802
   Proj_Maine_CS83_East =	11831
   Proj_Maine_CS83_West =	11832
   Proj_Maryland_CS27 =	11900
   Proj_Maryland_CS83 =	11930
   Proj_Massachusetts_CS27_Mainland =	12001
   Proj_Massachusetts_CS27_Island =	12002
   Proj_Massachusetts_CS83_Mainland =	12031
   Proj_Massachusetts_CS83_Island =	12032
   Proj_Michigan_State_Plane_East =	12101
   Proj_Michigan_State_Plane_Old_Central =	12102
   Proj_Michigan_State_Plane_West =	12103
   Proj_Michigan_CS27_North =	12111
   Proj_Michigan_CS27_Central =	12112
   Proj_Michigan_CS27_South =	12113
   Proj_Michigan_CS83_North =	12141
   Proj_Michigan_CS83_Central =	12142
   Proj_Michigan_CS83_South =	12143
   Proj_Minnesota_CS27_North =	12201
   Proj_Minnesota_CS27_Central =	12202
   Proj_Minnesota_CS27_South =	12203
   Proj_Minnesota_CS83_North =	12231
   Proj_Minnesota_CS83_Central =	12232
   Proj_Minnesota_CS83_South =	12233
   Proj_Mississippi_CS27_East =	12301
   Proj_Mississippi_CS27_West =	12302
   Proj_Mississippi_CS83_East =	12331
   Proj_Mississippi_CS83_West =	12332
   Proj_Missouri_CS27_East =	12401
   Proj_Missouri_CS27_Central =	12402
   Proj_Missouri_CS27_West =	12403
   Proj_Missouri_CS83_East =	12431
   Proj_Missouri_CS83_Central =	12432
   Proj_Missouri_CS83_West =	12433
   Proj_Montana_CS27_North =	12501
   Proj_Montana_CS27_Central =	12502
   Proj_Montana_CS27_South =	12503
   Proj_Montana_CS83 =	12530
   Proj_Nebraska_CS27_North =	12601
   Proj_Nebraska_CS27_South =	12602
   Proj_Nebraska_CS83 =	12630
   Proj_Nevada_CS27_East =	12701
   Proj_Nevada_CS27_Central =	12702
   Proj_Nevada_CS27_West =	12703
   Proj_Nevada_CS83_East =	12731
   Proj_Nevada_CS83_Central =	12732
   Proj_Nevada_CS83_West =	12733
   Proj_New_Hampshire_CS27 =	12800
   Proj_New_Hampshire_CS83 =	12830
   Proj_New_Jersey_CS27 =	12900
   Proj_New_Jersey_CS83 =	12930
   Proj_New_Mexico_CS27_East =	13001
   Proj_New_Mexico_CS27_Central =	13002
   Proj_New_Mexico_CS27_West =	13003
   Proj_New_Mexico_CS83_East =	13031
   Proj_New_Mexico_CS83_Central =	13032
   Proj_New_Mexico_CS83_West =	13033
   Proj_New_York_CS27_East =	13101
   Proj_New_York_CS27_Central =	13102
   Proj_New_York_CS27_West =	13103
   Proj_New_York_CS27_Long_Island =	13104
   Proj_New_York_CS83_East =	13131
   Proj_New_York_CS83_Central =	13132
   Proj_New_York_CS83_West =	13133
   Proj_New_York_CS83_Long_Island =	13134
   Proj_North_Carolina_CS27 =	13200
   Proj_North_Carolina_CS83 =	13230
   Proj_North_Dakota_CS27_North =	13301
   Proj_North_Dakota_CS27_South =	13302
   Proj_North_Dakota_CS83_North =	13331
   Proj_North_Dakota_CS83_South =	13332
   Proj_Ohio_CS27_North =	13401
   Proj_Ohio_CS27_South =	13402
   Proj_Ohio_CS83_North =	13431
   Proj_Ohio_CS83_South =	13432
   Proj_Oklahoma_CS27_North =	13501
   Proj_Oklahoma_CS27_South =	13502
   Proj_Oklahoma_CS83_North =	13531
   Proj_Oklahoma_CS83_South =	13532
   Proj_Oregon_CS27_North =	13601
   Proj_Oregon_CS27_South =	13602
   Proj_Oregon_CS83_North =	13631
   Proj_Oregon_CS83_South =	13632
   Proj_Pennsylvania_CS27_North =	13701
   Proj_Pennsylvania_CS27_South =	13702
   Proj_Pennsylvania_CS83_North =	13731
   Proj_Pennsylvania_CS83_South =	13732
   Proj_Rhode_Island_CS27 =	13800
   Proj_Rhode_Island_CS83 =	13830
   Proj_South_Carolina_CS27_North =	13901
   Proj_South_Carolina_CS27_South =	13902
   Proj_South_Carolina_CS83 =	13930
   Proj_South_Dakota_CS27_North =	14001
   Proj_South_Dakota_CS27_South =	14002
   Proj_South_Dakota_CS83_North =	14031
   Proj_South_Dakota_CS83_South =	14032
   Proj_Tennessee_CS27 =	14100
   Proj_Tennessee_CS83 =	14130
   Proj_Texas_CS27_North =	14201
   Proj_Texas_CS27_North_Central =	14202
   Proj_Texas_CS27_Central =	14203
   Proj_Texas_CS27_South_Central =	14204
   Proj_Texas_CS27_South =	14205
   Proj_Texas_CS83_North =	14231
   Proj_Texas_CS83_North_Central =	14232
   Proj_Texas_CS83_Central =	14233
   Proj_Texas_CS83_South_Central =	14234
   Proj_Texas_CS83_South =	14235
   Proj_Utah_CS27_North =	14301
   Proj_Utah_CS27_Central =	14302
   Proj_Utah_CS27_South =	14303
   Proj_Utah_CS83_North =	14331
   Proj_Utah_CS83_Central =	14332
   Proj_Utah_CS83_South =	14333
   Proj_Vermont_CS27 =	14400
   Proj_Vermont_CS83 =	14430
   Proj_Virginia_CS27_North =	14501
   Proj_Virginia_CS27_South =	14502
   Proj_Virginia_CS83_North =	14531
   Proj_Virginia_CS83_South =	14532
   Proj_Washington_CS27_North =	14601
   Proj_Washington_CS27_South =	14602
   Proj_Washington_CS83_North =	14631
   Proj_Washington_CS83_South =	14632
   Proj_West_Virginia_CS27_North =	14701
   Proj_West_Virginia_CS27_South =	14702
   Proj_West_Virginia_CS83_North =	14731
   Proj_West_Virginia_CS83_South =	14732
   Proj_Wisconsin_CS27_North =	14801
   Proj_Wisconsin_CS27_Central =	14802
   Proj_Wisconsin_CS27_South =	14803
   Proj_Wisconsin_CS83_North =	14831
   Proj_Wisconsin_CS83_Central =	14832
   Proj_Wisconsin_CS83_South =	14833
   Proj_Wyoming_CS27_East =	14901
   Proj_Wyoming_CS27_East_Central =	14902
   Proj_Wyoming_CS27_West_Central =	14903
   Proj_Wyoming_CS27_West =	14904
   Proj_Wyoming_CS83_East =	14931
   Proj_Wyoming_CS83_East_Central =	14932
   Proj_Wyoming_CS83_West_Central =	14933
   Proj_Wyoming_CS83_West =	14934
   Proj_Alaska_CS27_1 =	15001
   Proj_Alaska_CS27_2 =	15002
   Proj_Alaska_CS27_3 =	15003
   Proj_Alaska_CS27_4 =	15004
   Proj_Alaska_CS27_5 =	15005
   Proj_Alaska_CS27_6 =	15006
   Proj_Alaska_CS27_7 =	15007
   Proj_Alaska_CS27_8 =	15008
   Proj_Alaska_CS27_9 =	15009
   Proj_Alaska_CS27_10 =	15010
   Proj_Alaska_CS83_1 =	15031
   Proj_Alaska_CS83_2 =	15032
   Proj_Alaska_CS83_3 =	15033
   Proj_Alaska_CS83_4 =	15034
   Proj_Alaska_CS83_5 =	15035
   Proj_Alaska_CS83_6 =	15036
   Proj_Alaska_CS83_7 =	15037
   Proj_Alaska_CS83_8 =	15038
   Proj_Alaska_CS83_9 =	15039
   Proj_Alaska_CS83_10 =	15040
   Proj_Hawaii_CS27_1 =	15101
   Proj_Hawaii_CS27_2 =	15102
   Proj_Hawaii_CS27_3 =	15103
   Proj_Hawaii_CS27_4 =	15104
   Proj_Hawaii_CS27_5 =	15105
   Proj_Hawaii_CS83_1 =	15131
   Proj_Hawaii_CS83_2 =	15132
   Proj_Hawaii_CS83_3 =	15133
   Proj_Hawaii_CS83_4 =	15134
   Proj_Hawaii_CS83_5 =	15135
   Proj_Puerto_Rico_CS27 =	15201
   Proj_St_Croix =	15202
   Proj_Puerto_Rico_Virgin_Is =	15230
   Proj_BLM_14N_feet =	15914
   Proj_BLM_15N_feet =	15915
   Proj_BLM_16N_feet =	15916
   Proj_BLM_17N_feet =	15917
   Proj_Map_Grid_of_Australia_48 =	17348
   Proj_Map_Grid_of_Australia_49 =	17349
   Proj_Map_Grid_of_Australia_50 =	17350
   Proj_Map_Grid_of_Australia_51 =	17351
   Proj_Map_Grid_of_Australia_52 =	17352
   Proj_Map_Grid_of_Australia_53 =	17353
   Proj_Map_Grid_of_Australia_54 =	17354
   Proj_Map_Grid_of_Australia_55 =	17355
   Proj_Map_Grid_of_Australia_56 =	17356
   Proj_Map_Grid_of_Australia_57 =	17357
   Proj_Map_Grid_of_Australia_58 =	17358
   Proj_Australian_Map_Grid_48 =	17448
   Proj_Australian_Map_Grid_49 =	17449
   Proj_Australian_Map_Grid_50 =	17450
   Proj_Australian_Map_Grid_51 =	17451
   Proj_Australian_Map_Grid_52 =	17452
   Proj_Australian_Map_Grid_53 =	17453
   Proj_Australian_Map_Grid_54 =	17454
   Proj_Australian_Map_Grid_55 =	17455
   Proj_Australian_Map_Grid_56 =	17456
   Proj_Australian_Map_Grid_57 =	17457
   Proj_Australian_Map_Grid_58 =	17458
   Proj_Argentina_1 =	18031
   Proj_Argentina_2 =	18032
   Proj_Argentina_3 =	18033
   Proj_Argentina_4 =	18034
   Proj_Argentina_5 =	18035
   Proj_Argentina_6 =	18036
   Proj_Argentina_7 =	18037
   Proj_Colombia_3W =	18051
   Proj_Colombia_Bogota =	18052
   Proj_Colombia_3E =	18053
   Proj_Colombia_6E =	18054
   Proj_Egypt_Red_Belt =	18072
   Proj_Egypt_Purple_Belt =	18073
   Proj_Extended_Purple_Belt =	18074
   Proj_New_Zealand_North_Island_Nat_Grid =	18141
   Proj_New_Zealand_South_Island_Nat_Grid =	18142
   Proj_Bahrain_Grid =	19900
   Proj_Netherlands_E_Indies_Equatorial =	19905
   Proj_RSO_Borneo =	19912

+----------------------------------+
6.3.3.3 Coordinate Transformation Codes

Ranges:

   0 = undefined
   [    1, 16383] = GeoTIFF Coordinate Transformation codes
   [16384, 32766] = Reserved by GeoTIFF
   32767          = user-defined
   [32768, 65535] = Private User Implementations

Values:

   CT_TransverseMercator =	1
   CT_TransvMercator_Modified_Alaska = 2
   CT_ObliqueMercator =	3
   CT_ObliqueMercator_Laborde =	4
   CT_ObliqueMercator_Rosenmund =	5
   CT_ObliqueMercator_Spherical =	6
   CT_Mercator =	7
   CT_LambertConfConic_2SP =	8
   CT_LambertConfConic_Helmert =	9
   CT_LambertAzimEqualArea =	10
   CT_AlbersEqualArea =	11
   CT_AzimuthalEquidistant =	12
   CT_EquidistantConic =	13
   CT_Stereographic =	14
   CT_PolarStereographic =	15
   CT_ObliqueStereographic =	16
   CT_Equirectangular =	17
   CT_CassiniSoldner =	18
   CT_Gnomonic =	19
   CT_MillerCylindrical =	20
   CT_Orthographic =	21
   CT_Polyconic =	22
   CT_Robinson =	23
   CT_Sinusoidal =	24
   CT_VanDerGrinten =	25
   CT_NewZealandMapGrid =	26
   CT_TransvMercator_SouthOriented=	27

Aliases:

   CT_AlaskaConformal =		CT_TransvMercator_Modified_Alaska
   CT_TransvEquidistCylindrical =	CT_CassiniSoldner
   CT_ObliqueMercator_Hotine =	CT_ObliqueMercator
   CT_SwissObliqueCylindrical =	CT_ObliqueMercator_Rosenmund
   CT_GaussBoaga =			CT_TransverseMercator
   CT_GaussKruger =			CT_TransverseMercator
   CT_LambertConfConic = 		CT_LambertConfConic_2SP 
   CT_LambertConfConic_Helmert =	CT_LambertConfConic_1SP
   CT_SouthOrientedGaussConformal =	CT_TransvMercator_SouthOriented

+----------------------------------+
6.3.4 Vertical CS Codes
+----------------------------------+
6.3.4.1 Vertical CS Type Codes
Ranges:

   0               = undefined
   [    1,   4999] = Reserved
   [ 5000,   5099] = EPSG Ellipsoid Vertical CS Codes
   [ 5100,   5199] = EPSG Orthometric Vertical CS Codes
   [ 5200,   5999] = Reserved EPSG
   [ 6000,  32766] = Reserved
   32767           = user-defined
   [32768, 65535]  = Private User Implementations

Values:

   VertCS_Airy_1830_ellipsoid =	5001
   VertCS_Airy_Modified_1849_ellipsoid =	5002
   VertCS_ANS_ellipsoid =	5003
   VertCS_Bessel_1841_ellipsoid =	5004
   VertCS_Bessel_Modified_ellipsoid =	5005
   VertCS_Bessel_Namibia_ellipsoid =	5006
   VertCS_Clarke_1858_ellipsoid =	5007
   VertCS_Clarke_1866_ellipsoid =	5008
   VertCS_Clarke_1880_Benoit_ellipsoid =	5010
   VertCS_Clarke_1880_IGN_ellipsoid =	5011
   VertCS_Clarke_1880_RGS_ellipsoid =	5012
   VertCS_Clarke_1880_Arc_ellipsoid =	5013
   VertCS_Clarke_1880_SGA_1922_ellipsoid =	5014
   VertCS_Everest_1830_1937_Adjustment_ellipsoid =	5015
   VertCS_Everest_1830_1967_Definition_ellipsoid =	5016
   VertCS_Everest_1830_1975_Definition_ellipsoid =	5017
   VertCS_Everest_1830_Modified_ellipsoid =	5018
   VertCS_GRS_1980_ellipsoid =	5019
   VertCS_Helmert_1906_ellipsoid =	5020
   VertCS_INS_ellipsoid =	5021
   VertCS_International_1924_ellipsoid =	5022
   VertCS_International_1967_ellipsoid =	5023
   VertCS_Krassowsky_1940_ellipsoid =	5024
   VertCS_NWL_9D_ellipsoid =	5025
   VertCS_NWL_10D_ellipsoid =	5026
   VertCS_Plessis_1817_ellipsoid =	5027
   VertCS_Struve_1860_ellipsoid =	5028
   VertCS_War_Office_ellipsoid =	5029
   VertCS_WGS_84_ellipsoid =	5030
   VertCS_GEM_10C_ellipsoid =	5031
   VertCS_OSU86F_ellipsoid =	5032
   VertCS_OSU91A_ellipsoid =	5033

  Orthometric Vertical CS;

   VertCS_Newlyn =	5101
   VertCS_North_American_Vertical_Datum_1929 =	5102
   VertCS_North_American_Vertical_Datum_1988 =	5103
   VertCS_Yellow_Sea_1956 =	5104
   VertCS_Baltic_Sea =	5105
   VertCS_Caspian_Sea =	5106

+----------------------------------+
6.3.4.2 Vertical CS Datum Codes
Ranges:

   0               = undefined
   [    1,  16383] = Vertical Datum Codes
   [16384,  32766] = Reserved
   32767           = user-defined
   [32768, 65535]  = Private User Implementations

No vertical datum codes are currently defined, other than those implied by
the corrsponding Vertical CS code.

+--------------------------------------------------------------------+
+----------------------------------+
6.4 EPSG Geodesy Parameter Index
+----------------------------------+

Here is a summary of the index ranges for the various coding systems used by EPSG in their tables. A copy of this index may be acquired at the FTP sites mentioned in the references in section 5. The "value" table entries below describe how values from one table are related to codes from another table.

Summary
--------

   Entity                        digit   Range
   ----------------------------  ------- --------------	
   Prime Meridian                8       8000 thru 8999
   Ellipsoid                     7       7000 thru 7999
   Geodetic Datum                6       6000 thru 6999
   Vertical datum                5       5000 thru 5999
   Geographic Coordinate System  4       4000 thru 4999
   Projected Coordinate Systems  2 or 3  20000 thru 32760
   Map Projection                1       10000 - 19999

Geodetic Datum Codes
--------------------
   Datum Type                 Value     Range            Currently Defined
   -------------------------- --------- --------------   -----------------
   Unspecified Geodetic Datum [EC-1000] 6000 thru 6099   6001 thru 6035
   Geodetic Datum                       6100 thru 6321   6200 thru 6315
   WGS 72; WGS 72BE and WGS84           6322 thru 6327   6322 thru 6327
   Geodetic Datum (ancient)             6900 thru 6999   6901 thru 6902

   Note for Values: EC = corresponding Ellipsoid Code.

Vertical Datum Codes
--------------------
   Datum Type                 Value     Range            Currently Defined
   -------------------------- --------- --------------   -----------------     
   Ellipsoidal                [EC-1000] 5000 thru 5099   5001 thru 5035
   Orthometric                          5100 thru 5899   5101 thru 5106

   Note for Values: EC = corresponding Ellipsoid Code.

Geographic Coordinate System Codes    
----------------------------------
   GCS Type                    Value      Range           Currently Defined
   -----------------------     ---------- --------------  -----------------        
   Unknown geodetic datum      [GDC-2000] 4000 thru 4099  4001 thru 4045
   Known datum (Greenwich)     [GDC-2000] 4100 thru 4321  4200 thru 4315
   WGS 72; WGS 72BE and WGS84             4322 thru 4327  4322 thru 4327
   Known datum (not Greenwich)            4800 thru 4899  4801 thru 4812
   Known datum (ancient)       [GDC-2000] 4900 thru 4999  4901 thru 4902

   Note for Values: GDC = corresponding Geodetic Datum Code

Map Projection System Codes
---------------------------

   US State Plane  ( 10000-15999 )
      Format:     1sszz            
         where ss is USC&GS State code  01 thru 59  
         zz is (USC&GS zone code)      for NAD27 zones               
         zz is (USC&GS zone code + 30) for NAD83 zones

   Larger zoned systems ( 16000-17999 ) 
      System                            Format  zz Range
      --------------------------------  ------- -------
      UTM (North)                       160zz   01   60   
      UTM (South)                       161zz   01   60   
      zoned Universal Gauss-Kruger      162zz   04   32
      Universal Gauss-Kruger (unzoned)  163zz   04   3                  
      Australian Map Grid               174zz   48   58   
      Southern African STM              175zz   13   35 

   Smaller zoned systems  ( 18000-18999 ) 
       Format:  18ssz           
           where ss is sequential system number  01   18   
           z is zone code               
                     
   Single zone projections ( 19900-19999 )
        Format:   199ss          
           where ss is sequential system number  00   25

Projected Coordinate Systems
----------------------------      

For PCS utilising GeogCS with code in range 4201 through 4321 
(i.e. geodetic datum code 6201 through 6319):

   As far as is possible the PCS code will be of the format 
   gggzz where ggg is (geodetic datum code -6000) and zz is zone.               
                  
For PCS utilising GeogCS with code out of range 4201 through 4321
(i.e.geodetic datum code 6201 through 6319):
    PCS code 20xxx where xxx is a sequential number               

WGS72 / UTM North     322zz where zz is UTM zone number   32201   32260   
WGS72 / UTM South     323zz where zz is UTM zone number   32301   32360
WGS72BE / UTM North   324zz where zz is UTM zone number   32401   32460
WGS72BE / UTM South   325zz where zz is UTM zone number   32501   32560
WGS84 / UTM North     326zz where zz is UTM zone number   32601   32660
WGS84 / UTM South     327zz where zz is UTM zone number   32701   32760
US State Plane (NAD27)   267xx or 320xx where xx is a sequential number            
US State Plane (NAD83)   269xx or 321xx where xx is a sequential number            

   
   
+----------------------------------------------------------------------+
7  Glossary
   +--------------------------------------------------------------------+

ASCII: 	[American Standard Code for Information Interchange]  The predominant character set encoding of present-day computers. 

Cell:	A rectangular area in Raster space, in which a single pixel value is filled.

Code:	In GeoTIFF, a code is a value assigned to a GeoKey, and has one of 65536 possible values.

Coordinate System: 	A systematic way of assigning real (x,y,z..) coordinates to a surface or volume. In Geodetics the surface is an ellipsoid used to model the earth.

Datum: 	a mathematical approximation to all or part of the earth's surface. Defining a datum requires the definition of an ellipsoid, its location and orientation, as well as the area for which the datum is valid.

Device Space	A coordinate space referencing scanner, printers and display devices.

DOUBLE: 	8-byte IEEE double precision floating point.

Ellipsoid: 	A mathematically defined quadratic surface used to model the earth.

EPSG: 	European Petroleum Survey Group.

Flattening: 	For an ellipsoid with major and minor axis lengths (a,b), the flattening is defined by:, 

                                       f = (a - b)/a

	For the earth, the value of f is approximately 1/298.3

Geocoding: 	An image is geocoded if a precise algorithm for determining the earth-location of each point in the image is defined.

Geographic Coordinate System:	A Geographic CS consists of a well-defined ellipsoidal datum, a Prime Meridian, and an angular unit, allowing the assignment of a Latitude-Longitude (and optionally, geodetic height) vector to a location on earth.

GeoKey	In GeoTIFF, a GeoKey is equivalent in function to a TIFF tag, but uses a different storage mechanism.

Georeferencing: 	An image is georeferenced if the location of its pixels in some model space is defined, but the transformation tying model space to the earth is not known.

GeoTIFF:	A standard for storing georeference and geocoding information in a TIFF 6.0 compliant raster file.

Grid	A coordinate mesh upon which pixels are placed

IEEE 	Institute of Electrical and Electronics Engineers, Inc.

IFD:	In TIFF format, an Image File Directory, containing all the TIFF tags for one image in the file (there may be more than one).

Meridian: 	Arc of constant longitude, passing through the poles.

Model Space	A flat geometrical space used to model a portion of the earth.

Parallel: 	Lines of constant latitude, parallel to the equator.

Pixel:	A dimensionless point-measurement, stored in a raster file.
POSC:	Petrotechnical Open Software Corporation.

Prime Meridian: 	An arbitrarily chosen meridian, used as reference for all others, and defined as 0 degrees longitude.

Projection	A projection in GeoTIFF consists of a linear (X,Y) coordinate system, and a coordinate transformation method (such as Transverse Mercator) to tie this system to an unspecified Geographic CS..

Projected Coordinate System	The result of the application of a projection transformation of a Geographic coordinate system

 Raster Space:	A continuous planar space in which pixel values are visually realized.

RATIONAL:	In TIFF format, a RATIONAL value is a fractional value represented by the ratio of two unsigned 4-byte integers.

SDTS	The USGS Spatial Data Transmission Standard.

Tag: 	In TIFF format, a tag is packet of numerical or ASCII values, which have a numerical "Tag" ID indicating their information content.

TIFF: 	Acronym for Tagged Image File Format; a platform-independent, extensive specification for storing raster data and ancillary information in a single file.

USGS	US Geological Survey

+---------------------------------------------------------------------+, 
              END OF SPECIFICATION
+---------------------------------------------------------------------+