#835: v.out.ogr -c flag doesn't work?
--------------------+-------------------------------------------------------
Reporter: lutra | Owner: grass-dev@lists.osgeo.org
Type: defect | Status: new
Priority: normal | Milestone: 6.4.0
Component: Vector | Version: 6.4.0 RCs
Keywords: | Platform: Linux
Cpu: x86-32 |
--------------------+-------------------------------------------------------
When exporting with v.out.ogr, if the input layer has islands a message
show
"WARNING: The map contains islands. To preserve them in the output map,
use the -c flag"
but if used, the -c flag seems to have no effect in the resulting vector.
#835: v.out.ogr -c flag doesn't work?
---------------------+------------------------------------------------------
Reporter: lutra | Owner: grass-dev@lists.osgeo.org
Type: defect | Status: new
Priority: normal | Milestone: 6.4.0
Component: Vector | Version: 6.4.0 RCs
Resolution: | Keywords:
Platform: Linux | Cpu: x86-32
---------------------+------------------------------------------------------
Comment (by mmetz):
The -c flag only has an effect if some features of the selected type have
no category in the selected layer.
That warning can be misleading because islands consist of one or more
areas within a larger area. One island can consist of holes (areas that
don't have a centroid with category) and valid areas (with centroid and
category) at the same time, or only areas or only holes. If all areas in
all islands have a centroid with category, the -c flag will indeed have no
effect.
Tested with landuse in the Spearfish dataset, exporting to shapefile once
with once without -c flag. Holes are preserved with the -c flag, i.e.
appear as holes (not filled areas) surrounded by filled areas. Without the
-c flag, holes become valid areas that are displayed like any other area.
Displaying both shapefiles in QGIS, the one with holes preserved on top of
the other one with holes converted to areas, immediately shows the
differences between the two vectors.
You are right. I tested the spearfish dataset and it works fine. Probably
the vector I used before is not as I supposed. I'll make further tests but
I guess that meanwhile I can close this as invalid.