[GRASS5] How to patch vector maps?

GRASS GRASS developer
1

Hi,

at time I try to understand how to intersect vector maps
topologically correct. What I did (using the Spearfish dataset,
latest version from the web site):

v.patch in=soils,fields out=soilsfarms.patch
# here v.support would print tons of warnings as expected
v.spag -si soilsfarms.patch
v.support soilsfarms.patch op=build

Still many warnings appear - is intersecting not possible
without getting attribute problems? Or am I on the wrong
roads?

Thanks,

Markus

2

Hi Markus,

This is one function in the vector library that could do with improvement.

I find that there are *far* fewer problems if you work with polylines when intersecting. Attempts to patch polygon maps result in loss of some lines, principally simple islands. Then v.spag. This usually introduces many small lines of 2-3 points that are hard to find and eliminate. So, maybe backup the dig_att list, convert polygon data file to lines with v.area2line or v.polylines, then v.patch and v.spag, clean up with v.spag -i and v.clean, and change back to polygons with v.line2area or v.polylines. restore the dig_att file and build.

I was in fact pondering this very problem today. When I get back into coding in earnest in the new year, I was thinking that the various vector processing modules could do with re-arangement (for the 5.1 release of course). v.patch and v.spag (intersection) should be combined, possibly with various options, and v.clean and v.spag -i also should be combined into one module.

David

Markus Neteler wrote:

Hi,

at time I try to understand how to intersect vector maps
topologically correct. What I did (using the Spearfish dataset,
latest version from the web site):

v.patch in=soils,fields out=soilsfarms.patch
# here v.support would print tons of warnings as expected
v.spag -si soilsfarms.patch
v.support soilsfarms.patch op=build

Still many warnings appear - is intersecting not possible
without getting attribute problems? Or am I on the wrong
roads?

Thanks,

Markus
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3

Huidae or somebody else using r.topmodel

I would like to ask whether it would be possible to add some information
about the format of the
parameters and input file to the r.topmodel page, or at least to the
site
where such file can be viewed without downloading the original software?

Currently it appears to me that it is impossible to run this model in
GRASS without knowing
the original program, or am I missing something?

thank you very much,

Helena

if it is Markus Neteler wrote:

Hi,

at time I try to understand how to intersect vector maps
topologically correct. What I did (using the Spearfish dataset,
latest version from the web site):

v.patch in=soils,fields out=soilsfarms.patch
# here v.support would print tons of warnings as expected
v.spag -si soilsfarms.patch
v.support soilsfarms.patch op=build

Still many warnings appear - is intersecting not possible
without getting attribute problems? Or am I on the wrong
roads?

Thanks,

Markus
_______________________________________________
grass5 mailing list
grass5@grass.itc.it
http://grass.itc.it/mailman/listinfo/grass5