I am attempting to create a predictive model for my study area. I have 10m DEMs which I have merged together using the Mosaic to New Raster tool (Picture 1). I am now trying to use the Slope and Aspect tools on the Merged DEMs. While the tools run successfully, noticeable lines appear after each time I run it (Pictures 2). I can only add two photos, but he Aspect has the same lines in it.

Picture 1. Snapshot of larger merged DEM image. Picture 2. Results of Slope tool at same location as Picture 1.

I am at a complete loss. Did I incorrectly merge the DEMs? I went through numerous renditions of merging before finding something that a) didn't completely wash out the terrain, and b) didn't have noticeable merge lines.

  • Are the lines in the same position as the boundaries between the DEMs you have merged? – Sam3000 Feb 24 '17 at 21:22
  • Yes and no. A few of the lines appear to correspond with where the DEMS overlap (e.g., the vertical line running down the center of picture 2). However, other lines do not appear to be related (e.g., the red horizontal line in the upper-left corner of Picture 2). Smaller squares are visible elsewhere that also appear to be independent of where DEMs overlap. Assuming some are from overlap, what would you suggest? – SpencerL Feb 24 '17 at 21:32
  • Hmm, do you remember what "Mosaic Operator" you used to create the final DEM? (2nd to last parameter of the Mosaic to New Raster Tool). That said, if those lines are appearing in seemingly random places this might not be a merge issue at all. – Sam3000 Feb 24 '17 at 21:44
  • Create hillshade of a single raster, if you see similar straight line, sources are of poor quality – FelixIP Feb 24 '17 at 21:47
  • For the attached pictures, I used the default option "LAST". I believe I used Blend and Sum options on other attempts that resulted in somewhat similar issues. – SpencerL Feb 24 '17 at 21:49

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