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I need to create an Hillshade from a DEM. The DEM has a projected CRS and I have performed Calculate Statistics before running the Hillshade tool. I am using ArcGIS 10.3 and I have Spatial Analyst enabled.

When I run Hillshade from the toolbox, the raster that is created has not values ranging from 0 to 254, but has values ranging from 124 to 220.

What causes this "strange" beahaviour of the hillshade function? Is there a way to produce an hillshade raster with proper values?

EDIT: if I activate "Use Hillshade effect" on the DEM, I get a series of squares that are really not good looking (like in this post Understanding garbage hillshade output from ArcGIS for Desktop?)

the derived hillshade seems ok instead, it doesn't show this problem

  • The values correspond to illumination. There's no requirement that the output be scaled to some arbitrary range. – Vince Jan 10 at 11:44
  • @Vince you are right, but when you create an hillshade, the info says "The hillshade raster has an integer value range of 0 to 255.". So I guess I'll always obtain a raster with the full possible values. Am I wrong? – Vale Jan 10 at 11:47
  • @BERA yes I am drawing the hillshade as stretched. I have performed a "Calculate Statistics" on the hillshade, and in Properties>Source>Statistics the max and min values are reported as 124 and 220. – Vale Jan 10 at 12:06
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    The algorithm, which is well documented, generates an 8-bit integer, but there's no requirement that the full range of that type be used. It would be a violation of the concept of hillshade to stretch the values. – Vince Jan 10 at 12:12
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    @Vince thanks I'll check the documentation. So my hillshade is fine. I thought that deriving from a DEM that cannot display as "use an hillshade effect" properly, not having the full possibile values could derive from it. I guess I'll post another question about the DEM – Vale Jan 10 at 12:17

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