I've been struggling with this problem for awhile. Here is a curvature raster to illustrate the problem https://i.sstatic.net/7RVrs.jpg

I'm using 10m DEM rasters from the NRCS Data Gateway for a large portion of California. The problem is some strange tiling that appears after merging, but isn't present in the original data (before merging). The grids create low points, so flow accumulation etc is drawn into them.

I've tried mosaic to new raster, create raster catalog and filter in ArcGIS 10.2, merge and build vrt in Qgis2.4 but the problem persists throughout.

When the license frees up, I'm going to try Merge and Filter (production mapping) and see if that works.

Am I just merging files wrong? Are these edge effects from merging tiles?

  • Are the rasters you are attempting to merge dems or curvature rasters derived from dems? Commented Oct 10, 2014 at 3:23
  • The rasters are DEM, the curvature in the link is just to illustrate what happens. That grid shows up in slope as well. Eventually the goal is to have a slope model for this large portion of CA for some slope stability models.
    – Rocksyeaa
    Commented Oct 10, 2014 at 16:18
  • The 10m DEM product is over-extrapolated and as such, there is notable contour biasing. Without smoothing, I do not consider them usable in geomorphometric applications. I would recommend using the 30m product. Commented Apr 19, 2018 at 15:56

1 Answer 1


Wondering if the issue could be with rasters that are derived from elevations (curvature) rather than the original dem data. Some issue similar to hill shade rasters, which can be problematic to mosaic as mentioned here

'HILLSHADE NOTE: (Do not MOSAIC hillshades: MOSAIC the DEM's first and then create a hillshade). When working with multiple DEM files, it is important to MOSAIC the individual DEM files before creating a hillshade. A hillshade process cannot create any 'shading' at the edges of the dataset (there is nothing to compare the edge cells with). This will create data gaps if two hillshades are MOSAICed - even if the original DEM files did not have a gap..'

  • It happens with slope too, but I havent tried to only mosaic, its always been mosaic to new raster. I'll try it now.
    – Rocksyeaa
    Commented Oct 10, 2014 at 16:09

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