Micha Silver wrote: > Bryan Keith wrote: >>> >>> Orange boundaries are duplicates - overlapping lines - that GRASS >>> topology doesn't allow. >>> You should be able to get rid of these with: >>> "v.clean in=... out=... tool=break,bpol,rmdupl" >>> But I've never had good luck with this. >>> The alternative that might work better for you: >>> Re-import the layer from the original shapefiles (or where ever they >>> came from) but use the "type=line" option to v.in.ogr. (No centroids >>> will be created) >>> Now do v.clean on this new GRASS vector, using tool=snap,break,rmdupl. >>> Next use >>> "v.type ... type=line,boundary" >>> to convert the (cleaned) lines to boundaries, and then >>> "v.centroids ... opt=add" >>> to create area centroids inside each closed boundary. >>> >> >> Micha, >> >> Yes, thank you, that worked! Here's what I did: >> >> > > Cheers. > Although I think I misled you a bit. I was mistaken about the orange line > color in the digitizer. It simply indicates a boundary that is wholly shared > by two adjacent areas. *Not* a topological error. > In any case, importing polygon shapefiles first as lines (not boundaries), > doing the topology cleanup, and then convert to boundaries and add centroids > seems to be the smoother way to go.
I object because 1. you would need to replicate the cleaning steps done by v.in.ogr which has, amongst others, a snapping option 2. adding centroids will add centroids to all areas, also those that where holes in polygons provided by OGR, e.g. a waterbodies shapefile with lakes and islands in lakes: the islands are not waterbodies and should not get a centroid 3. you will loose attributes because there is no (easy) way to link any attributes coming with the shapefile to newly generated centroids, e.g. land cover/land use shapefiles Markus M >> >> v.in.ogr -o dsn=C:\path\to\shapefile\test_ln.shp output=testm_ln type=line >> v.clean input=testm_ln output=testmclean_ln tool=snap,break,rmdupl >> thresh=0.2,0,0 >> v.type input=testmclean_ln output=testmclean_bnd type=line,boundary >> v.centroids input=testmclean_bnd output=testmclean_py option=add >> >> Thanks for all the help. >> >> Bryan >> -- >> > > Micha Silver > Arava Development Co. +972-52-3665918 > http://surfaces.co.il > > > _______________________________________________ > grass-user mailing list > [email protected] > http://lists.osgeo.org/mailman/listinfo/grass-user > _______________________________________________ grass-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-user
