GDAL-RASTER-SLOPE(1) GDAL GDAL-RASTER-SLOPE(1)
gdal-raster-slope - Generate a slope map
Added in version 3.11.
Usage: gdal raster slope [OPTIONS] <INPUT> <OUTPUT>
Generate a slope 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)
--unit <UNIT> Unit in which to express slopes. UNIT=degree|percent (default: degree)
--xscale <XSCALE> Ratio of vertical units to horizontal X axis units
--yscale <YSCALE> Ratio of vertical units to horizontal Y axis units
--gradient-alg <GRADIENT-ALG> Algorithm used to compute terrain gradient. GRADIENT-ALG=Horn|ZevenbergenThorne (default: Horn)
--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 slope generates a slope map, from any GDAL-supported
elevation raster.
This subcommand is also available as a potential step of gdal raster
pipeline
It generates a 32-bit float raster with slope values. You have the
option of specifying the type of slope value you want: degrees or
percent slope. In cases where the horizontal units differ from the
vertical units, you can also supply scaling factors to account for
differences between vertical and horizontal units.
The value -9999 is used as the output nodata value. A nodata value in
the target dataset will 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.
In general, it assumes that x, y and z units are identical. However,
if none of --xscale and --yscale are specified, and the CRS is a
geographic or projected CRS, it will automatically determine the
appropriate ratio from the units of the CRS, as well as the potential
value of the units of the raster band (as returned by
GDALRasterBand::GetUnitType(), if it is metre, foot international or
US survey foot). Note that for geographic CRS, the result for source
datasets at high latitudes may be incorrect, and prior reprojection
to a polar projection might be needed using gdal raster reproject.
If x (east-west) and y (north-south) units are identical, but z
(elevation) units are different, the --xscale and --yscale can be
used to set the ratio of vertical units to horizontal. For
geographic CRS near the equator, where units of latitude and units of
longitude are similar, elevation (z) units can be converted to be
compatible by using scale=370400 (if elevation is in feet) or
scale=111120 (if elevation is in meters). For locations not near the
equator, the --xscale value can be taken as the --yscale value
multiplied by the cosine of the mean latitude of the raster.
-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 slope must be
computed.
--unit degree|percent
Unit in which to express slopes. Defaults to degree.
--xscale <scale>
Ratio of vertical units to horizontal X axis units. If the
horizontal unit of the source DEM is degrees (e.g Lat/Long
WGS84 projection), you can use scale=111120 if the vertical
units are meters (or scale=370400 if they are in feet).
If none of --xscale and --yscale are specified, and the CRS is
a geographic or projected CRS, gdal raster slope will
automatically determine the appropriate ratio from the units
of the CRS, as well as the potential value of the units of the
raster band (as returned by GDALRasterBand::GetUnitType(), if
it is metre, foot international or US survey foot). Note that
for geographic CRS, the result for source datasets at high
latitudes may be incorrect, and prior reprojection to a polar
projection might be needed.
If --xscale is specified, --yscale must also be specified.
--yscale <scale>
Ratio of vertical units to horizontal Y axis units. If the
horizontal unit of the source DEM is degrees (e.g Lat/Long
WGS84 projection), you can use scale=111120 if the vertical
units are meters (or scale=370400 if they are in feet)
If none of --xscale and --yscale are specified, and the CRS is
a geographic or projected CRS, gdal raster slope will
automatically determine the appropriate ratio from the units
of the CRS, as well as the potential value of the units of the
raster band (as returned by GDALRasterBand::GetUnitType(), if
it is metre, foot international or US survey foot). Note that
for geographic CRS, the result for source datasets at high
latitudes may be incorrect, and prior reprojection to a polar
projection might be needed.
If --yscale is specified, --xscale must also be specified.
--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.
--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 a slope map from a DTED0 file.
$ gdal raster slope n43.dt0 out.tif --overwrite
Even Rouault <even.rouault@spatialys.com>
1998-2026
March 20, 2026 GDAL-RASTER-SLOPE(1)
NAME
gdal-raster-slope - Generate a slope map
Added in version 3.11.
SYNOPSIS
Usage: gdal raster slope [OPTIONS] <INPUT> <OUTPUT>
Generate a slope 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)
--unit <UNIT> Unit in which to express slopes. UNIT=degree|percent (default: degree)
--xscale <XSCALE> Ratio of vertical units to horizontal X axis units
--yscale <YSCALE> Ratio of vertical units to horizontal Y axis units
--gradient-alg <GRADIENT-ALG> Algorithm used to compute terrain gradient. GRADIENT-ALG=Horn|ZevenbergenThorne (default: Horn)
--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 slope generates a slope map, from any GDAL-supported
elevation raster.
This subcommand is also available as a potential step of gdal raster
pipeline
It generates a 32-bit float raster with slope values. You have the
option of specifying the type of slope value you want: degrees or
percent slope. In cases where the horizontal units differ from the
vertical units, you can also supply scaling factors to account for
differences between vertical and horizontal units.
The value -9999 is used as the output nodata value. A nodata value in
the target dataset will 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.
In general, it assumes that x, y and z units are identical. However,
if none of --xscale and --yscale are specified, and the CRS is a
geographic or projected CRS, it will automatically determine the
appropriate ratio from the units of the CRS, as well as the potential
value of the units of the raster band (as returned by
GDALRasterBand::GetUnitType(), if it is metre, foot international or
US survey foot). Note that for geographic CRS, the result for source
datasets at high latitudes may be incorrect, and prior reprojection
to a polar projection might be needed using gdal raster reproject.
If x (east-west) and y (north-south) units are identical, but z
(elevation) units are different, the --xscale and --yscale can be
used to set the ratio of vertical units to horizontal. For
geographic CRS near the equator, where units of latitude and units of
longitude are similar, elevation (z) units can be converted to be
compatible by using scale=370400 (if elevation is in feet) or
scale=111120 (if elevation is in meters). For locations not near the
equator, the --xscale value can be taken as the --yscale value
multiplied by the cosine of the mean latitude of the raster.
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 slope must be
computed.
--unit degree|percent
Unit in which to express slopes. Defaults to degree.
--xscale <scale>
Ratio of vertical units to horizontal X axis units. If the
horizontal unit of the source DEM is degrees (e.g Lat/Long
WGS84 projection), you can use scale=111120 if the vertical
units are meters (or scale=370400 if they are in feet).
If none of --xscale and --yscale are specified, and the CRS is
a geographic or projected CRS, gdal raster slope will
automatically determine the appropriate ratio from the units
of the CRS, as well as the potential value of the units of the
raster band (as returned by GDALRasterBand::GetUnitType(), if
it is metre, foot international or US survey foot). Note that
for geographic CRS, the result for source datasets at high
latitudes may be incorrect, and prior reprojection to a polar
projection might be needed.
If --xscale is specified, --yscale must also be specified.
--yscale <scale>
Ratio of vertical units to horizontal Y axis units. If the
horizontal unit of the source DEM is degrees (e.g Lat/Long
WGS84 projection), you can use scale=111120 if the vertical
units are meters (or scale=370400 if they are in feet)
If none of --xscale and --yscale are specified, and the CRS is
a geographic or projected CRS, gdal raster slope will
automatically determine the appropriate ratio from the units
of the CRS, as well as the potential value of the units of the
raster band (as returned by GDALRasterBand::GetUnitType(), if
it is metre, foot international or US survey foot). Note that
for geographic CRS, the result for source datasets at high
latitudes may be incorrect, and prior reprojection to a polar
projection might be needed.
If --yscale is specified, --xscale must also be specified.
--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.
--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 slope map from a DTED0 file.
$ gdal raster slope n43.dt0 out.tif --overwrite
AUTHOR
Even Rouault <even.rouault@spatialys.com>
COPYRIGHT
1998-2026
March 20, 2026 GDAL-RASTER-SLOPE(1)