Friday, October 23, 2009

More Watershed Analysis

I have downloaded 3-meter resolution NED files from the USDA Geospatial Data Gateway. I have mosaicked the ones from my study area, and extracted a smaller area of the mosaic using a mask.

I have run the hydrology tools on this NED, and have had much better results than with the first DEMs (10 meter resolution). I want to run them using pour points instead of the area-wide tools I've been using, see how those results compare with my current results.

My main problem is, the textbook I'm using doesn't go into as much depth as I'd like on this subject. It references other works, but so far I haven't gotten my hands on them. I have questions regarding the accuracy of the watershed analysis tools. My watersheds almost, but not quite, agree with the hydrology unit layer I've downloaded from the USDA website. I've downloaded both the 8- and 12- digit layers. What do GIS analysts do when confronted with this kind of conflict?

I've been spending all my time on the watershed analysis tools, and I need to get busy with the basics - land use, etc.

Bob Capezza is supposed to send me the 2009 NAIP files for Vermilion Parish via DVD. I've downloaded the 2007 layer, which is the latest available on the USDA web site.

I need to contact the Abbeville NRCS and Farm Service people on the land use data because previous GIS information on Coulee Baton was lost in a computer crash.

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