R: Hill shading

shade {terra} | R Documentation

## Hill shading

### Description

Compute hill shade from slope and aspect layers (both in radians). Slope and aspect can be computed with function `terrain`.

A hill shade layer is often used as a backdrop on top of which another, semi-transparent, layer is drawn.

### Usage

    shade(slope, aspect, angle=45, direction=0, normalize=FALSE, filename="", ...)

### Arguments

`slope` | SpatRasterwith slope values (in radians)
`aspect` | SpatRaster with aspect values (in radians)
`angle` | The the elevation angle of the light source (sun), in degrees
`direction` | The direction (azimuth) angle of the light source (sun), in degrees
`normalize` | Logical. If `TRUE`, values below zero are set to zero and the results are multiplied with 255
`filename` | character. Output filename
`...` | additional arguments for writing files as in `writeRaster`

### References

Horn, B.K.P., 1981. Hill shading and the reflectance map. Proceedings of the IEEE 69(1):14-47

### See Also

`terrain`

### Examples

    f <- system.file("ex/elev.tif", package="terra")
    r <- rast(f)
    alt <- disaggregate(r, 10, method="bilinear")
    slope <- terrain(alt, 'slope')
    aspect <- terrain(alt, 'aspect')
    hill <- shade(slope, aspect, 40, 270)
    plot(hill, col=grey(0:100/100), legend=FALSE, mar=c(2,2,1,4))
    plot(alt, col=rainbow(25, alpha=0.35), add=TRUE)

[Package terra version 1.3-22 Index]