topic Re: Flow Direction tool produces erroneous lines in output raster in ArcGIS Spatial Analyst Questions

Flow Direction tool produces erroneous lines in output raster

Anonymous User — Fri, 19 Apr 2013 21:49:16 GMT

Original User: jonathankoehler

I am running the Flow Direction tool on a seamless bare-earth NED raster elevation grid. The tool runs fine, but the output raster has a series of horizontal and vertical lines - like a grid - that contain erroneous flow directions, and therefore make the layer useless for generating watersheds. Attached are a couple of picture of what the output rasters look like - one is from a 1m DEM and the other is from a 10m. These lines are not visible in the raw DEM file, so it appears that something about the Flow Direction tool brings them out or creates them.

I have tried running Flow Direction with several DEM resolutions including 10m, 30m, and 1m LiDAR with the same results. I have also tried running it with and without first using the Fill tool to clean it up - it doesn't seem to make any difference.

I'm using using ArcGIS Desktop 10 SP 5, ArcInfo license. Any help would be greatly appreciated. Thanks,

Jonathan

[ATTACH=CONFIG]23682[/ATTACH][ATTACH=CONFIG]23683[/ATTACH]

Re: Flow Direction tool produces erroneous lines in output raster

Anonymous User — Fri, 19 Apr 2013 22:54:32 GMT

Original User: MBoucher21

I've seen this problem addressed in the Forum before. From a quick search I couldn't find that post.

Re: Flow Direction tool produces erroneous lines in output raster

EricRice — Mon, 22 Apr 2013 18:39:16 GMT

Please show us a Hillshade from that DEM. If it is gridded like your flow direction raster then you or someone has most likely projected the data with Nearest Neighbor resampling. If it wasn't projected, and some other resampling was done to change cell sizes, using Nearest would still cause this. The NED FAQ has a topic on this.

http://ned.usgs.gov/faq.asp#RESAMPLE

If your DEM is "old" by USGS standards, then striping can be there too. See http://ned.usgs.gov/about.asp

ArcGIS doesn't cause these artifacts.

Best,
Eric