[GRASS-user] Determine surface areas

Nikolaus Arnold ich at the-masterplan.net
Fri Mar 6 13:04:40 EST 2009

Finally got it.

Import map:

created areas:
v.type input=map1 output=map2 type=line,boundary
v.clean input=map2 output=map3 tool=snap thresh=0.0001
v.centroids input=map3 output=map4 option=add

checked with v.digit (strangely v.centroids always categorized in the same
way, but in the outer ring it mixed up two areas, but that was easily
corrected by manually changing those two categories)

v.to.rast use=cat

masked with rastermap - watercellvalue


thanks a lot

Am Freitag, 6. März 2009 09:25:45 schrieb Markus Metz:
> Moritz Lennert wrote:
> > On 05/03/09 23:15, ich at the-masterplan.net wrote:
> >> Hi!
> >>
> >> I am still working on the extended problem and so far i have done the
> >> following.
> >> I created circles and sectors in autocad and imported the dxf file
> >> (first
> >> one sector at a time).
> >> The import didn't seem to work that well, so i converted lines to
> >> boundaries and used v.clean to get areas, and inserted a centroid with
> >> v.digit and created a rastermap with v.to.rast (source: val, and
> >> featuretype area).
> >> using the rastermap as mask I can use r.report or r.stats to get the
> >> waterarea/watercells.
> >>
> >> Because there are 160 of these areas i was wondering if there is a
> >> possibility to use all of the areas at once (or at least more than
> >> one at
> >> a time) assign some kind of an ID to every area and get the results
> >> separately for every area.
> >> trying to use more than one area at a time always got me the total 
> >> for all areas.
> >
> > Just give each centroid a different category value (e.g. using
> > v.category, or by hand using v.digit), then v.to.rast use=cat. Then
> > r.stats/r.report should give you the result by category.
> Or v.to.db option=area?
> Markus M

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