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I have been trying to greatly reduce or eliminate the contour-like texture that appears in my output from gdaldem slope. The image, below, demonstrates this textural effect.

Output from <code>gdaldem slope</code>, demonstrating the textural effect I am trying to reduce

The texture of the slope values appears to follow the contours, making a terraced effect. I am curious, does this output reflect a reasonable calculation of slope (e.g. reasonable isoclines)? Or are these patterns an artifact?

Is it possible that I will not be able to eliminate this effect because this texture is present in the original DEM (image, below)?

enter image description here

I have tried a number of suggestions for reducing patterns in the slope values, for instance:

Also, I have seen this texture in many other slope rasters, see for example:

Any ideas on what causes this?

  • Similar to gis.stackexchange.com/questions/140026/… perhaps, where did your DEM come from? Is it interpolated from contours? – Michael Stimson Apr 17 '18 at 22:56
  • The DEM was obtained in an *.adf format from the National Map download utility and is identified as "U.S. Geological Survey, 2013, USGS NED n41w125 1/3 arc-second 2013 1 x 1 degree ArcGrid: U.S. Geological Survey." I warped/projected the DEM from NAD83 (EPSG 4269) into UTM Zone 10N (EPSG 21690) so the horizontal and vertical units would be consistent. The DEM was not interpolated from contours, so the 'gdal_grid' algorithm wasn't used and it would be unclear to me if the question you refer to is similar. – keek3 Apr 18 '18 at 1:01

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