Geographic Information Systems Stack Exchange is a question and answer site for cartographers, geographers and GIS professionals. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I have been attempting to calculate a slope raster in ArcGis 10, and have been encountering a problem where cells which previously had data appear as no data cells in a few places on the raster following the completion of the reclassification tool process.

To attempt to solve this we have run the IsNull tool on the original elevation raster to identify where no data cells are. We next ran focal statistics to calculate the mean value of a 50x50 cell rectangle surrounding the no-data cells. This filled in all the no-data cells. Following this we ran the slope tool. The end result every time has fairly large irregular rectangles scattered around the raster with no-data values. What might be the problem here?

share|improve this question
Sorry I didn't realize I needed to do that. Thanks. – J_L Dec 20 '12 at 20:15
When you say "cells which previously had data appear as no data" do you mean, they had data in the DEM? What is the projection of your DEM? Is it in a geographic coordinate system? If so, you will need to reproject it to a projected coordinate system and recalculate the slope. This may be the problem. – Fezter Dec 21 '12 at 1:44

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Browse other questions tagged or ask your own question.