[GRASS-user] r.proj input output comparison

Martin du Saire mdusaire at umn.edu
Thu Oct 19 12:53:38 EDT 2006


A specific, and general question on reprojection:

I've changed the resolution of a raster from 1000 to 2 (UTM15) using 
r.proj.  The summary statistics are very similar for both rasters 
which is reassuring.  However, how do I display/compare both rasters 
so that I can see which of the higher resolution pixels have the 
largest/smallest differences (for example) with respect to the 
original 1000 m data?

The importance of "knowing your projections" was discussed in the UTM 
concepts thread, but in general how would one compare reprojected 
maps to evaluate projection related differences?

Or, if I have a set of images, vectors, and raster that "line up" 
correctly in one projection, wouldn't they be self-consistent when 
reprojected, although somewhat distorted with respect to the original?



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