# `gdal raster tri`

Added in version 3.11.

Generate a Terrain Ruggedness Index (TRI) map

## Synopsis

    Usage: gdal raster tri [OPTIONS] <INPUT> <OUTPUT>

    Generate a Terrain Ruggedness Index (TRI) map

    Positional arguments:
      -i, --input <INPUT>                                  Input raster datasets [required]
      -o, --output <OUTPUT>                                Output raster dataset [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]
      -q, --quiet                                          Quiet mode (no progress bar)

    Options:
      -f, --of, --format, --output-format <OUTPUT-FORMAT>  Output format ("GDALG" allowed)
      --co, --creation-option <KEY>=<VALUE>                Creation option [may be repeated]
      --overwrite                                          Whether overwriting existing output is allowed
                                                           Mutually exclusive with --append
      --append                                             Append as a subdataset to existing output
                                                           Mutually exclusive with --overwrite
      -b, --band <BAND>                                    Input band (1-based index) (default: 1)
      --algorithm <ALGORITHM>                              Algorithm to compute TRI. ALGORITHM=Riley|Wilson (default: Riley)
      --no-edges                                           Do not try to interpolate values at dataset edges or close to nodata values

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

## Description

gdal raster tri generates a single-band raster with values computed from the elevation. TRI stands for Terrain Ruggedness Index, which measures the difference between a central pixel and its surrounding cells.

This subcommand is also available as a potential step of gdal raster pipeline

Value -9999 is used as the nodata value.

A nodata value in the target dataset will also be emitted if at least one pixel set to the nodata value is found in the 3x3 window centered around each source pixel. By default, the algorithm will compute values at image edges or if a nodata value is found in the 3x3 window, by interpolating missing values, unless `--no-edges` is specified, in which case a 1-pixel border around the image will be set with the nodata value.

### Standard options

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

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

--co <NAME>=<VALUE>

  Many formats have one or more optional creation options that can be used to control particulars about the file created. For instance, the GeoTIFF driver supports creation options to control compression, and whether the file should be tiled.

  May be repeated.

  The 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 Raster drivers format specific documentation for legal creation options for each format.

--overwrite

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

-b, --band <BAND>

  Index (starting at 1) of the band to which the TRI must be computed.

--algorithm Riley|Wilson

  Select the algorithm to use:

  - `Riley`, the default, uses the square root of the sum of the square of the difference between a central pixel and its surrounding cells. This is recommended for terrestrial use cases. It is implemented from Riley, S.J., De Gloria, S.D., Elliot, R. (1999): A Terrain Ruggedness that Quantifies Topographic Heterogeneity. Intermountain Journal of Science, Vol.5, No.1-4, pp.23-27

  - `Wilson` uses the mean difference between a central pixel and its surrounding cells. This is recommended for bathymetric use cases. It is implemented from Wilson et al. 2007, Marine Geodesy 30:3-35.

--no-edges

  Do not try to interpolate values at dataset edges or close to nodata values

## 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 raster dataset using the GDALG: GDAL Streamed Algorithm driver, and apply the specified pipeline in a on-the-fly / streamed way.

## Examples

### Example 1: Generates a Terrain Ruggedness Index (TRI) map from a DTED0 file.

    $ gdal raster tri n43.dt0 out.tif --overwrite