A large rectangular polygon dataset is used with ~14 000 features.
Polygons are first processed with rmarea to remove all polygons of size
900 m2. Then a simplification is executed with v.generalize using a factor
of 10, all other parameters defaulted.
After simplification several large polygons are missing from the set
rendering it useless.
System is a win7x64; QGIS 2.6.1 and GRASS 6.4.4
Dataset can be provided upon request (being a 7.5mb shapefile).
Replying to [ticket:2550 dido]:
> Polygons disappear after v.generalize simplification.
>
> A large rectangular polygon dataset is used with ~14 000 features.
> Polygons are first processed with rmarea to remove all polygons of size
900 m2. Then a simplification is executed with v.generalize using a factor
of 10, all other parameters defaulted.
>
> After simplification several large polygons are missing from the set
rendering it useless.
>
> System is a win7x64; QGIS 2.6.1 and GRASS 6.4.4
>
> Dataset can be provided upon request (being a 7.5mb shapefile).
>
I assume the workflow is v.in.ogr + v.clean tool=rmarea + v.generalize
threshold=10.
Several functions relating to v.generalize have just been fixed in trunk
and I would like to test. Can you please provide a link to the shapefile
or send the shapefile to markus.metz.giswork at gmail dot com? Thanks!
Replying to [ticket:2550 dido]:
> Polygons disappear after v.generalize simplification.
>
> A large rectangular polygon dataset is used with ~14 000 features.
> Polygons are first processed with rmarea to remove all polygons of size
900 m2. Then a simplification is executed with v.generalize using a factor
of 10, all other parameters defaulted.
>
> After simplification several large polygons are missing from the set
rendering it useless.
I can confirm the problem. This is a bug in the vector libraries regarding
topology updating and has been fixed in GRASS 7. Please wait for GRASS
7.0.0RC2 or use a daily build.