Aspect

Draft: written, not yet checked by a person Operation · aspect

The compass direction each cell of an elevation raster faces downhill.

Pitfall. Flat cells have no aspect, and engines mark them with different special values; check before averaging.

About this operation
Also called	slope direction, facing direction, gdaldem aspect
Group	`raster/terrain`
Checks	`crs.geographic, raster.nodata`
Pitfalls	1 listed above
Columbus tool	`raster_op · aspect`
Notes	Not stated
Status	active
Broader	Not stated
Narrower	Not stated
Related	`slope` `hillshade`

Parameters

Name	Type	Required	Default	Values	Note
`z_unit`	enum	yes	Not stated	`m, ft, us-ft`	Not stated
`band`	integer	no	Not stated	Not stated	Not stated

Direction	Name	Type	Geometry	Note
Input	`raster`	raster	Not stated	An elevation model.
Output	`output`	raster	Not stated	Not stated

Engine	Tool	Parameters	Differences
`gdal`	`gdal raster aspect`	`z_unit` Aspect does not depend on the elevation unit. `band` → `band` `raster` → `input` `output` → `output`	convention chooses compass bearings (azimuth, the default) or mathematical angles.
`grass`	`r.slope.aspect`	`z_unit` always crs-units. Elevation is taken in the project's horizontal units; otherwise set zscale. `raster` → `elevation` `output` → `aspect`	Without the n flag, aspect is counterclockwise from east (east 0, north 90); this mapping sets it, for compass bearings (north 0, clockwise). Preset: `{"flag_n":true}`
`postgis-raster`	`st_aspect`	`band` → `nband` `raster` → `rast`	None noted
`qgis`	`native:aspect`	`raster` → `INPUT` `output` → `OUTPUT`	None noted
`terra`	`terra::terrain`	`z_unit` always crs-units. Elevation must be in the map units, or metres when the CRS is longitude/latitude. `raster` → `x`	None noted Preset: `{"v":"aspect","unit":"degrees"}`
`whiteboxtools`	`Aspect`	`raster` → `dem` `output` → `output`	None noted
`xarray-spatial`	`xrspatial.aspect`	`z_unit` always crs-units. With the default method = 'planar', elevations must be in the same units as the cell size; z_unit applies only with method = 'geodesic'. `raster` → `agg`	Takes an xarray DataArray with x and y coordinates; edge cells are NaN by default (boundary = 'nan').