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Compute a Slope Raster from a DEM

get_slope.Rd

Computes a slope raster (in degrees) either by:

  • downloading a DEM automatically using x, or

  • using a DEM raster supplied manually through the dem argument.

Usage

get_slope(x = NULL, dem = NULL, agg = 5, verbose = TRUE, ...)

Arguments

x

sf or sfc; Geometry located in France.

dem

SpatRaster representing ground elevation (DEM). Must be supplied only when x is NULL.

agg

numeric; Target resolution (in meters) to which the DEM is aggregated if its native resolution is finer. Default: 5.

verbose

logical; If TRUE, display messages.

...

Additional parameters passed to get_dem() when x is supplied.

Value

A SpatRaster containing slope values in degrees.

Details

When x is provided, the DEM is obtained with get_dem(), using by default a resolution equal to agg. When x is not provided, a DEM must be supplied via dem.

If the DEM resolution is finer than agg, the raster is aggregated to avoid artefacts and reduce computation time.

Slope is computed with terra::terrain() using Horn's 8-neighbor algorithm, and returned in degrees.

Aggregation is performed with terra::aggregate() using a mean function. This is recommended when high-resolution DEMs (<5 m) would otherwise generate line artefacts.

Examples

if (FALSE) { # \dontrun{
# Automatic download mode
s <- get_slope(x = my_polygon, buffer = 200)

# Manual mode
dem <- get_dem(my_polygon)
s <- get_slope(dem = dem)
} # }