# `gdal vector geom buffer`

Added in version 3.11.

Compute a buffer around geometries of a vector dataset.

## Synopsis

    Usage: gdal vector geom buffer [OPTIONS] <INPUT> <OUTPUT> <DISTANCE>

    Compute a buffer around geometries of a vector dataset.

    Positional arguments:
      -i, --input <INPUT>                                  Input vector datasets [required]
      -o, --output <OUTPUT>                                Output vector dataset [required]
      --distance <DISTANCE>                                Distance to which to extend the geometry. [required]

    Common Options:
      -h, --help                                           Display help message and exit
      --json-usage                                         Display usage as JSON document and exit
      --config <KEY>=<VALUE>                               Configuration option [may be repeated]
      --progress                                           Display progress bar

    Options:
      -l, --layer, --input-layer <INPUT-LAYER>             Input layer name(s) [may be repeated]
      -f, --of, --format, --output-format <OUTPUT-FORMAT>  Output format ("GDALG" allowed)
      --co, --creation-option <KEY>=<VALUE>                Creation option [may be repeated]
      --lco, --layer-creation-option <KEY>=<VALUE>         Layer creation option [may be repeated]
      --overwrite                                          Whether overwriting existing output is allowed
      --update                                             Whether to open existing dataset in update mode
      --overwrite-layer                                    Whether overwriting existing layer is allowed
      --append                                             Whether appending to existing layer is allowed
      --output-layer <OUTPUT-LAYER>                        Output layer name
      --active-layer <ACTIVE-LAYER>                        Set active layer (if not specified, all)
      --active-geometry <ACTIVE-GEOMETRY>                  Geometry field name to which to restrict the processing (if not specified, all)
      --endcap-style <ENDCAP-STYLE>                        Endcap style.. ENDCAP-STYLE=round|flat|square (default: round)
      --join-style <JOIN-STYLE>                            Join style.. JOIN-STYLE=round|mitre|bevel (default: round)
      --mitre-limit <MITRE-LIMIT>                          Mitre ratio limit (only affects mitered join style). (default: 5)
      --quadrant-segments <QUADRANT-SEGMENTS>              Number of line segments used to approximate a quarter circle. (default: 8)
      --side <SIDE>                                        Sets whether the computed buffer should be single-sided or not.. SIDE=both|left|right (default: both)

    Advanced Options:
      --if, --input-format <INPUT-FORMAT>                  Input formats [may be repeated]
      --oo, --open-option <KEY>=<VALUE>                    Open options [may be repeated]

## Description

gdal vector geom buffer computes a POLYGON or MULTIPOLYGON that represents all points whose distance from a geometry/geography is less than or equal to a given distance. A negative distance shrinks the geometry rather than expanding it. A negative distance may shrink a polygon completely, in which case POLYGON EMPTY is returned. For points and lines negative distances always return empty results.

See https://postgis.net/docs/ST_Buffer.html for graphical illustrations of the effect of the different parameters.

This command can also be used as a step of gdal vector pipeline.

Note

This command requires a GDAL build against the GEOS library.

### Standard options

-f, --of, --format, --output-format <OUTPUT-FORMAT>

  Which output vector format to use. Allowed values may be given by `gdal --formats | grep vector | grep rw | sort`

--co <NAME>=<VALUE>

  Many formats have one or more optional dataset creation options that can be used to control particulars about the file created. For instance, the GeoPackage driver supports creation options to control the version.

  May be repeated.

  The dataset creation options available vary by format driver, and some simple formats have no creation options at all. A list of options supported for a format can be listed with the --formats command line option but the documentation for the format is the definitive source of information on driver creation options. See Vector drivers format specific documentation for legal creation options for each format.

  Note that dataset creation options are different from layer creation options.

-lco <NAME>=<VALUE>

  Layer creation option (format specific)

-lco <NAME>=<VALUE>

  Layer creation option (format specific)

--overwrite

  Allow program to overwrite existing target file or dataset. Otherwise, by default, gdal errors out if the target file or dataset already exists.

--active-layer <ACTIVE-LAYER>

  Set the active layer. When it is specified, only the layer specified by its name will be subject to the processing. Other layers will be not modified. If this option is not specified, all layers will be subject to the processing.

--active-geometry <ACTIVE-GEOMETRY>

  Set the active geometry field from its name. When it is specified, only the specified geometry field will be subject to the processing. Other geometry fields will be not modified. If this option is not specified, all geometry fields will be subject to the processing. This option can be combined together with `--active-layer`.

--distance <DISTANCE>

  Radius of the buffer around the input geometry. The unit of the distance is in georeferenced units of the source layer.

--endcap-style round|flat|square

  Specifies the end cap style of the generated buffer. Default is `round`.

--join-style round|mitre|bevel

  Sets the join style for outside (reflex) corners between line segments. Default is `round`.

--mitre-limit <MITRE-LIMIT>

  Sets the limit on the mitre ratio used for very sharp corners.

  Default is 5.

  The mitre ratio is the ratio of the distance from the corner to the end of the mitred offset corner. When two line segments meet at a sharp angle, a miter join will extend far beyond the original geometry. (and in the extreme case will be infinitely far.) To prevent unreasonable geometry, the mitre limit allows controlling the maximum length of the join corner. Corners with a ratio which exceed the limit will be beveled.

--quadrant-segments <QUADRANT-SEGMENTS>

  Sets the number of line segments used to approximate an angle fillet in round joins.

  This determines the maximum error in the approximation to the true buffer curve. The default value of 8 gives less than 2% max error in the buffer distance. For a max error of < 1%, use QS = 12. For a max error of < 0.1%, use QS = 18. The error is always less than the buffer distance (in other words, the computed buffer curve is always inside the true curve).

--side both|left|right

  Sets whether the computed buffer should be single-sided or on both side (default).

  `left` (resp. `right`) means that buffer is on the left-hand

    (resp. right-hand) side of the line when following it in the order of its vertices.

  Single-side buffering is only applicable to LINESTRING geometry and does not affect POINT or POLYGON geometries, and the end cap style is forced to square.

### Advanced options

--oo <NAME>=<VALUE>

  Dataset open option (format specific).

  May be repeated.

--if <format>

  Format/driver name to be attempted to open the input file(s). It is generally not necessary to specify it, but it can be used to skip automatic driver detection, when it fails to select the appropriate driver. This option can be repeated several times to specify several candidate drivers. Note that it does not force those drivers to open the dataset. In particular, some drivers have requirements on file extensions.

  May be repeated.

## GDALG output (on-the-fly / streamed dataset)

This program supports serializing the command line as a JSON file using the `GDALG` output format. The resulting file can then be opened as a vector dataset using the GDALG: GDAL Streamed Algorithm driver, and apply the specified pipeline in a on-the-fly / streamed way.

## Examples

### Example 1: Compute a buffer of one km around input geometries (assuming the CRS is in meters)

    $ gdal vector geom buffer --distance=1000 in.gpkg out.gpkg --overwrite