[GRASS-user] Non-Topological Vector Polygon Layer From r.water.outlet

[Moritz Lennert]

Le Wed, 26 Oct 2016 08:37:38 -0600,
Phillip Allen <phillipjallen830 at gmail.com> a écrit :

> Hi,
> 
> I have a point layer file that represents stream sediment sample
> locations. My goal is to create watershed basins for each sample
> location using r.water.outlet or r.stream.basins, then convert to a
> vector layer and finally have them reside in a PostGIS table with all
> the other associated sample data. I have run the points through
> r.stream.snap so they now fall exactly only the DEM drainage.
> 
> Grass normally operates with topology but in this case I need a
> non-topological vector polygon layer. Stream sediment samples are
> often collected every 1-5km or more along any particular drainage so
> the basins must overlap.
> 
> What is the best strategy to deal with generating an overlapping
> polygon layer? I have only approximately 10,000 stream sediment
> samples this time but there are always more!

See Markus Metz' answer in a similar thread from two days ago:

http://lists.osgeo.org/pipermail/grass-user/2016-October/075475.html

As in his message: it is possible to handle overlapping polygons using
cat numbers, but the first question is: what do you want to do with the
data ?

Moritz