topic Re: How to Check if Raster Flow Accumulation Process is becoming Corrupted in ArcGIS Spatial Analyst Questions

How to Check if Raster Flow Accumulation Process is becoming Corrupted

SpatiallySpeaking — Fri, 24 Jun 2011 19:52:58 GMT

Hi,

I have been trying to create a flow accumulation raster from a filled flow direction DEM. I initially ran the Flow Accumulation tool using a 90m DEM, which completed in less than five minutes. I have now been trying to run the Flow Accumulation tool for a 20m DEM for the same, small area. I have tried running it overnight on the same machine that calculated the 90m DEM in mere minutes, bu it never completes.

It seems (to me) that this 20m DEM should have completed relatively quickly as well. Since ArcMap has no useful status bar it seems there is no way to tell if the tool is making progress. I have turned off background processing and looked in the results window, but there is no indication of percent progress. Is there anyway to check if the process has become hung or if it just needs more than eight hours to process?

The 20m DEM is roughly 600 x 500 cells; 1.29 MB.

Thank you,

Dan

Re: How to Check if Raster Flow Accumulation Process is becoming Corrupted

SpatiallySpeaking — Fri, 24 Jun 2011 23:17:34 GMT

...and here is the example (plus another for one, which has the same issue; attached) in case anyone knows of a way to check for file corruption.

Re: How to Check if Raster Flow Accumulation Process is becoming Corrupted

JeffLee — Wed, 29 Jun 2011 01:48:54 GMT

Daniel;

Flow accumulation grids are generated from a 8 point flow direction grid. I have downloaded one of your rasters and I see that the values range from 1 to 255. Starting from the East, the values for the flow direction grid should be 1, 2, 4, 8, 16, 32, 64 and 128. I suspect that the flow direction grid that you have uploaded were generated from an unfilled DEM, thus explaining the values that I am seeing.