[GRASS-user] v.generalize failing on some geoms

Paolo Cavallini cavallini at faunalia.it
Sat Feb 10 23:45:35 PST 2018

Thanks Markus for the hint.
Replies below.

Il 10/02/2018 22:53, Markus Metz ha scritto:
> This seems to be a reprojection problem.
> If you reprojected the vector data in GRASS with v.in.ogr + v.proj, this
> is a problem of GRASS, granted that v.in.ogr did not complain about
> vector topology.
> If you reprojected non-topological polygons, this is a common problem
> when reprojecting non-topological polygons. Please import these polygons
> first into GRASS, then reproject within GRASS and run v.generalize on
> the reprojected GRASS vector.

I'm not explicitly reprojecting it. I tried the command from within
QGIS>Processing. Here the relevant commands:

g.proj -c proj4="+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0
+x_0=0.0 +y_0=0 +k=1.0 +units=m +nadgrids=@null +wktext +no_defs"
v.in.ogr min_area=0.0001 snap=-1
layer=1518196447.565 output=tmp1518196448046 --overwrite -o
g.region n=5538851.39594 s=5150937.66442 e=1377191.37538 w=1004373.60434
v.generalize input="tmp1518196448046" method=douglas threshold="1000"
look_ahead="7" reduction="50" -l
output="output081005b4fafd473bbfa438a964de80f1" --overwrite

All the best.
Paolo Cavallini - www.faunalia.eu
QGIS & PostGIS courses: http://www.faunalia.eu/training.html

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