[GRASS5] a request to fix v.cutter bug
michael.barton at asu.edu
Wed Mar 10 12:23:30 EST 2004
In helping students with an overlay assignment for my spatial
technologies class, it became apparent that they were getting strange
results in trying to clip a set of state-wide soil and geology maps
with the boundary of a national forest here in Arizona. A series of
soil and geology polygons simply were not being clipped--i.e., ignored
Last night I did a lot of exploratory work and finally realized that
this is due to a known bug in v.cutter. According to the manual...
- - - -
There are a few rare situations that are not currently handled
correctly. These mostly involve nodes or vertices intersecting exactly
with lines of the opposite map. You will know you have hit one of
these cases because a lot of strange text will start spitting out.
Borders between areas with the same attributes are not dissolved.
There are many places where the code could be optimized greatly.
- - - -
It turns out that the soil and geology polygons stop at the Arizona
state border. The National Forest boundary also stops at the Arizona
state border. This apparently is enough of an overlap to cause v.cutter
to ignore those polygons.
v.cutter is one of the few and very important geoprocessing tools in
the GRASS vector toolbox. IMHO, it is important for it to work
correctly. I don't know if this bug is corrected in version 5.7
(hopefully Radim can enlighten here). However, I want to make a plea
that it be fixed if possible in both 5.3 and 5.7.
Michael Barton, Professor & Curator
Department of Anthropology
Arizona State University
Tempe, AZ 85287-2402
voice: 480-965-6262; fax: 480-965-7671
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