GDAL-RASTER-ASPECT(1) GDAL GDAL-RASTER-ASPECT(1)
gdal-raster-aspect - Generate an aspect map
Added in version 3.11.
Usage: gdal raster aspect [OPTIONS] <INPUT> <OUTPUT>
Generate an aspect 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)
--convention <CONVENTION> Convention for output angles. CONVENTION=azimuth|trigonometric-angle (default: azimuth)
--gradient-alg <GRADIENT-ALG> Algorithm used to compute terrain gradient. GRADIENT-ALG=Horn|ZevenbergenThorne (default: Horn)
--zero-for-flat Whether to output zero for flat areas
--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]
gdal raster aspect generates an aspect map, from any GDAL-supported
elevation raster.
This subcommand is also available as a potential step of gdal raster
pipeline
It outputs a 32-bit float raster with values between 0<degree> and
360<degree> representing the azimuth that slopes are facing. The
definition of the azimuth is such that: - 0<degree> means that the
slope is facing the North, - 90<degree> it's facing the East, -
180<degree> it's facing the South - and 270<degree> it's facing the
West (provided that the top of your input raster is north oriented).
The aspect value -9999 is used as the nodata value to indicate
undefined aspect in flat areas with slope=0.
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.
-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, --creation-option <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 aspect must be
computed.
--convention azimuth|trigonometric-angle
Convention for output angles.
Defaults to azimuth, that is to say: - 0<degree> means that
the slope is facing the North, - 90<degree> it's facing the
East, - 180<degree> it's facing the South - and 270<degree>
it's facing the West (provided that the top of your input
raster is north oriented).
If set to trigonometric-angle, - 0<degree> means that the
slope is facing the East, - 90<degree> it's facing the North,
- 180<degree> it's facing the West - and 270<degree> it's
facing the South
--gradient-alg Horn|ZevenbergenThorne
Algorithm used to compute terrain gradient. The default is
Horn. The literature suggests Zevenbergen & Thorne to be more
suited to smooth landscapes, whereas Horn's formula to perform
better on rougher terrain.
--zero-for-flat
Whether to output zero for flat areas. By default, flat areas
where the slope is null will be assigned a nodata value
(-9999). When setting this option, they are set to 0.
--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.
Example 1: Generates an aspect map from a DTED0 file.
$ gdal raster aspect n43.dt0 out.tif --overwrite
Even Rouault <even.rouault@spatialys.com>
1998-2026
March 20, 2026 GDAL-RASTER-ASPECT(1)
NAME
gdal-raster-aspect - Generate an aspect map
Added in version 3.11.
SYNOPSIS
Usage: gdal raster aspect [OPTIONS] <INPUT> <OUTPUT>
Generate an aspect 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)
--convention <CONVENTION> Convention for output angles. CONVENTION=azimuth|trigonometric-angle (default: azimuth)
--gradient-alg <GRADIENT-ALG> Algorithm used to compute terrain gradient. GRADIENT-ALG=Horn|ZevenbergenThorne (default: Horn)
--zero-for-flat Whether to output zero for flat areas
--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 aspect generates an aspect map, from any GDAL-supported
elevation raster.
This subcommand is also available as a potential step of gdal raster
pipeline
It outputs a 32-bit float raster with values between 0<degree> and
360<degree> representing the azimuth that slopes are facing. The
definition of the azimuth is such that: - 0<degree> means that the
slope is facing the North, - 90<degree> it's facing the East, -
180<degree> it's facing the South - and 270<degree> it's facing the
West (provided that the top of your input raster is north oriented).
The aspect value -9999 is used as the nodata value to indicate
undefined aspect in flat areas with slope=0.
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, --creation-option <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 aspect must be
computed.
--convention azimuth|trigonometric-angle
Convention for output angles.
Defaults to azimuth, that is to say: - 0<degree> means that
the slope is facing the North, - 90<degree> it's facing the
East, - 180<degree> it's facing the South - and 270<degree>
it's facing the West (provided that the top of your input
raster is north oriented).
If set to trigonometric-angle, - 0<degree> means that the
slope is facing the East, - 90<degree> it's facing the North,
- 180<degree> it's facing the West - and 270<degree> it's
facing the South
--gradient-alg Horn|ZevenbergenThorne
Algorithm used to compute terrain gradient. The default is
Horn. The literature suggests Zevenbergen & Thorne to be more
suited to smooth landscapes, whereas Horn's formula to perform
better on rougher terrain.
--zero-for-flat
Whether to output zero for flat areas. By default, flat areas
where the slope is null will be assigned a nodata value
(-9999). When setting this option, they are set to 0.
--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 an aspect map from a DTED0 file.
$ gdal raster aspect n43.dt0 out.tif --overwrite
AUTHOR
Even Rouault <even.rouault@spatialys.com>
COPYRIGHT
1998-2026
March 20, 2026 GDAL-RASTER-ASPECT(1)