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I just started to use raster files, and I want to create a Terrain Ruggedness Index (TRI), using QGIS. Which layers must I use? Do I need to create the "Input file (DEM raster)" (in: Raster>Analysis>DEM (Terrain Models), or is it OK to use only a raster layer with elevation for each pixel?

  • Thank you! The problem is, when I use the raster layer with elevation data to create a TRI (using QGIS), I get a interval of 0-22.16, and since I know it goes up to >600m, I don't know how to interpret this result or what is it I am doing wrong.. – Teresa May 24 '16 at 13:40
  • According to the document I quote you must be in level terrain, check the document it states how to interpret the results – Gerardo Jimenez May 24 '16 at 13:47
  • So the interval I get [0-22.16] is in meters, and I should fit this in the Roughness Index? And I just realized I get different results if I use TRI or Roughness (in DEM (Terrain models)>Mode); which one shoud I use for this index? – Teresa May 24 '16 at 14:57
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    from gdal.org/gdaldem.html: This command outputs a single-band raster with values computed from the elevation. Roughness is the largest inter-cell difference of a central pixel and its surrounding cell, as defined in Wilson et al (2007, Marine Geodesy 30:3-35). – Gerardo Jimenez May 24 '16 at 16:30

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