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I created a DEM in ArcMap (10.3) using Topo to Raster. Then, when I tried to create a hillshade using spatial analyst, result look like the picture below. Any idea on what causing the contour-like artifact? The profile graph on the left represents the values of the hillshade along the black line, while the graph on the right represents the DEM values at the same location. enter image description here

  • This page will give you some insight into why it looks different. – Hornbydd Apr 29 '15 at 10:23
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    I hate to be the bearer of bad news but the fault here lies with your DEM and not the hillshade tool. Your DEM was likely created by interpolating contour line data and what you're seeing is the artifact of this process. You'll either need to re-interpolate the data (if you have access to it) or look for another source of elevation data. Often these types of artifacts are more apparent in terrain derivatives (e.g. slope, curvature, hillshade, etc.) than the DEM itself. – WhiteboxDev Apr 29 '15 at 11:25
  • Thank you for the comments! Yes, I also believed that it was the problem of DEM as it was created from contour line. I had re-interpolate the data with DEM sampling points, and the artifact was gone. – Mang Cheuk May 1 '15 at 3:09
  • @WhiteboxDev - You should consider posting your comment as an answer buddy =) – Joseph May 1 '15 at 9:04
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    @Joseph Looks like the issue was resolved and FelixP did a good job of providing an answer...he even quoted one of my favourite all-time GIS texts. – WhiteboxDev May 1 '15 at 11:36
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The isoline paper maps are usually the cheapest and quite often the only available sources of information on the spatial pattern of terrain altitude, rain intensity, snow depth and many other phenomenon. Unfortunately “…interpolating digitized contours to a regular grid can result in the creation of severe artefacts in this resulting surface. Curiously enough, the more care that is taken to digitize a contour line with many sampled points, the greater the problem. ...commercial GIS may include procedures for interpolating from contours.“ Burrough, P.A., McDonnell R.A. Principles of Geographical Information Systems. Oxford University Press, 1998. ISBN 0-19-823365-5 (Pbk), p. 128

We are lucky to have advanced topo to raster tool, but as one can see even it does not eliminate artefacts completely

  • Thanks for your answer. I tried re-interpolate the DEM with sampling points, rather than contour lines. The artifact disappeared. – Mang Cheuk May 1 '15 at 3:11
  • Good . However if it is about hydrology, stick to contours and Topo to raster. Helps to reduce non-existing sinks – FelixIP May 2 '15 at 22:27

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