The hillshade function produces a grayscale 3D representation of the terrain surface, with the sun's relative position taken into account for shading the image. Hillshading is a technique for visualizing terrain determined by a light source and the slope and aspect of the elevation surface. It is a qualitative method for visualizing topography and does not give absolute elevation values.
This function provides two options for generating hillshades: traditional and multidirectional. The traditional method calculates the hillshade using an illumination source from one direction using the altitude and azimuth properties to specify the sun's position. The multidirectional method combines light from multiple sources to represent the hillshaded terrain. The advantage of the multidirectional hillshade method is that more detail is displayed in areas typically affected by oversaturation and deep shadows than when using the traditional hillshade method.
The primary and most immediate advantage of a hillshade is its ability to display raw elevation data in a way that our brains are used to dealing with. The image above is what the raw data looks like, and while it is possible to make general observations it is virtually impossible to pick out any small-scale elevation variations.
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