On Sun, Dec 2, 2012 at 3:33 PM, Benjamin Ducke <[email protected]> wrote: > Hi List -- > > Looking at function centroid() in geom.c > of v.in.ogr, it seems to me that the code > for import of polygons always assumes that > the first ring is the exterior boundary and > the following ones are all interior boundaries > (see comment on lines 70 and 71). > > Is this a limitation of GRASS' vector model > or would it be possible to import multi-part > polygons with more than one outer boundary by > amending the code in v.in.ogr?
Import of multi-features such as wkbGeometryCollection, wkbMultiPolygon, wkbMultiLineString, wkbMultiPoint is supported by v.in.ogr. For centroid(), see lines 160ff, for geom(), see lines 432ff. > > I understand that it is possible to import > multi-part geometries into GRASS and assign > each part the same "cat" number. However, > when exporting with v.out.ogr, they will be > exported as separate parts, each with its > own attribute table row. Is there any > way to preserve multi-part features using > v.in.ogr and v.out.ogr? Multi-part features are preserved by v.in.ogr, all included features get the same category. For v.out.ogr, I think this is not so easy because not every OGR-supported output format supports multi-features (may be wrong). > > If this is currently not possible: Would it > be a viable solution to add a "-j" (join) > flag to v.out.ogr so that it will merge > geometries with the same "cat" into multi- > part features on export? I guess technically yes, if multi-features are supported by the selected output format. Markus M _______________________________________________ grass-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-user
