[R-sig-Geo] clipping SpatialPolygonsDataFrames

[Anthony Fischbach]

Thank you Tom!
I tried the rgeos::gIntersection() approach on a quad dual core Windows 7
workstation, but found that it choked on a TopologyException after running
for over 10 minutes.

The raster approach to the problem produced a clean result in 77 seconds,
requiring under a single day of processing to handle each of my study areas
across the study years.  This now seems reasonable.

I then implemented this in Python for ArcGIS and found that the polygon
clipping required less than 7 seconds, reducing my process time to a little
over 3 hours.

O.K. then, perhaps its best to perform the GIS overlay with Python / ArcGIS
for now and then bring the results back into R from there.



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Tony Fischbach, Wildlife Biologist
Walrus Research Program
Alaska Science Center
U.S. Geological Survey
4210 University Drive
Anchorage, AK 99508-4650

AFischbach at usgs.gov
http://alaska.usgs.gov/science/biology/walrus
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