On 19/03/08 04:18, Andrew Schroeder wrote:
Hi Everyone,
Can you tell me if GRASS is able to detect change between two input
polyline shapefiles? I have a 5m contour set for two different years at
a particular mine, and I'm looking for a way to automate detection of
the yearly pit advances.
Basically, I'm looking for something to subtract file A from file B
(b-a=change) and output a file showing just the lines that changed
between the two files.
Thanks for any direction you can offer.
IIUC, this would be a classic example of v.overlay usage, only that
v.overlay does not support two line maps (i.e. not line + line, only
area + point/line/area). I don't really know why this is so.
If your contours are closed you could transform them into areas and then
run v.overlay with operator=not.
Moritz
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