I have two elevation datasets which I am trying to subtract to calculate thickness (using ArcGIS raster calculator). The first datset is a tif which is oriented north-south and has a cell size of 5 ft x 5 ft. The second data set is a surfer grid which has a cell size of 10 ft x 10 ft but is rotated by approximately 30 degrees to the east. When I subtract the two rasters, I select bilinear re-sampling in the environments section of raster calculator. However, when I spot check my resulting output raster of thickness, I often get a thickness that is vastly underestimated (e.g. thickness should be 10 ft but the raster output equals a thickness of 2). Strangely enough, other cells that I spot check will have a thickness that is close to what I expect. I also re-ran the same calculation but used nearest neighbor re-sampling; I got the exact same results.

What is causing this discrepancy? Is it the rotated grid? How can I fix this?

closed as unclear what you're asking by PolyGeo Sep 17 '16 at 9:01

Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

  • 1
    Could you explain why the surfer grid is rotated 30 deg east? Did you set the snap raster environment? Are both datasets in the same projected coordinate system? – Aaron Feb 15 '16 at 18:52
  • 2
    try to resample (and reproject if necessary) the the 10ft raster to 5ft and make sure you snap it to the other raster. This way you can make sure the right values are subtracted. It will also be easier for you validate the results – Thomas Feb 15 '16 at 20:21