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.
Andrew Schroeder
Just an idea:
v.surf.rst/idw/etc for both datasets
r.mapcalc diff=old-new
cell area*diff sum
Maris.
2008/3/19, Andrew Schroeder <andrew_schroeder@charoneconcepts.com>:
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.
Andrew Schroeder
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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