Yes, and in fact the PostGIS geomunion function uses the "diss" field just fine to group by. --
On Tue, Oct 20, 2009 at 4:24 PM, M S <[email protected]> wrote: > If you query two adjacent polygons, do they both have the same value > for the 'diss' attribute? > > On Tue, Oct 20, 2009 at 7:05 PM, Roger André <[email protected]> wrote: >> Yeah, kinda long, but here it is. fwiw, I loaded the file into >> PostGIS and let it crank away at the dissolve. Was done after about >> an hour, so while I'm thrilled to have the correct data, I'd still >> like to figure out a solution in GRASS. >> >>> v.dissolve global_mask out=new_mask col=diss --o >> 100% >> Building topology for vector map <new_mask_18169>... >> Registering primitives... >> 5450 primitives registered >> 288073 vertices registered >> Building areas... >> 100% >> 2723 areas built >> 2721 isles built >> Attaching islands... >> 100% >> Attaching centroids... >> 100% >> Number of nodes: 5448 >> Number of primitives: 5450 >> Number of points: 0 >> Number of lines: 0 >> Number of boundaries: 2727 >> Number of centroids: 2723 >> Number of areas: 2723 >> Number of isles: 2721 >> v.reclass complete. 2723 features reclassed. >> WARNING: Vector map <new_mask> already exists and will be overwritten >> Extracting features... >> Building topology for vector map <new_mask>... >> Registering primitives... >> 5450 primitives registered >> 288073 vertices registered >> Building areas... >> 100% >> 2723 areas built >> 2721 isles built >> Attaching islands... >> 100% >> Attaching centroids... >> 100% >> Number of nodes: 5448 >> Number of primitives: 5450 >> Number of points: 0 >> Number of lines: 0 >> Number of boundaries: 2727 >> Number of centroids: 2723 >> Number of areas: 2723 >> Number of isles: 2721 >> Writing attributes... >> Removing duplicate centroids... >> Building topology for vector map <new_mask>... >> Registering primitives... >> 5450 primitives registered >> 288073 vertices registered >> Building areas... >> 100% >> 2723 areas built >> 2721 isles built >> Attaching islands... >> 100% >> Attaching centroids... >> 100% >> Number of nodes: 5448 >> Number of primitives: 5450 >> Number of points: 0 >> Number of lines: 0 >> Number of boundaries: 2727 >> Number of centroids: 2723 >> Number of areas: 2723 >> Number of isles: 2721 >> >> >> On Tue, Oct 20, 2009 at 1:47 PM, MS <[email protected]> wrote: >>> Is there output for the dissolve command? >>> >>> Mark >>> >>> On Oct 20, 2009, at 4:37 PM, Roger André <[email protected]> wrote: >>> >>>> Hi all, >>>> >>>> I'm having trouble creating a single, dissolved feature and exporting >>>> it as a multipolygon. Here is what I've done: >>>> >>>> - layer I started with: >>>>> >>>>> v.info -t global_mask >>>> >>>> nodes=5448 >>>> points=0 >>>> lines=0 >>>> boundaries=2727 >>>> centroids=2723 >>>> areas=2723 >>>> islands=2721 >>>> faces=0 >>>> kernels=0 >>>> primitives=5450 >>>> map3d=0 >>>> >>>> - added dissolve field: >>>>> >>>>> v.db.addcol global_mask col="diss int" >>>>> v.db.update global_mask col=diss value=1 >>>> >>>> - check that diss field is there: >>>>> >>>>> v.info -c global_mask >>>> >>>> Displaying column types/names for database connection of layer 1: >>>> INTEGER|cat >>>> DOUBLE PRECISION|cat_ >>>> INTEGER|diss >>>> >>>> - dissolve: >>>> v.dissolve global_mask out=new_mask col=diss --o >>>> >>>> - inspect new layer: >>>>> >>>>> v.info -t new_mask >>>> >>>> nodes=5448 >>>> points=0 >>>> lines=0 >>>> boundaries=2727 >>>> centroids=2723 >>>> areas=2723 >>>> islands=2721 >>>> faces=0 >>>> kernels=0 >>>> primitives=5450 >>>> map3d=0 >>>> >>>> - export layer as shapefile: >>>>> >>>>> v.out.ogr -p input=new_mask type=area dsn=/tmp olayer=new_mask >>>> >>>> - check new shapefile: >>>> ogrinfo -summary /tmp new_mask >>>> INFO: Open of `/tmp' >>>> using driver `ESRI Shapefile' successful. >>>> >>>> Layer name: new_mask >>>> Geometry: Polygon >>>> Feature Count: 2723 >>>> Extent: (-180.000000, -90.000000) - (180.000000, 83.623596) >>>> Layer SRS WKT: >>>> GEOGCS["GCS_WGS_1984", >>>> DATUM["WGS_1984", >>>> SPHEROID["WGS_1984",6378137,298.257223563]], >>>> PRIMEM["Greenwich",0], >>>> UNIT["Degree",0.017453292519943295]] >>>> cat: Real (11.0) >>>> >>>> As you can see, I still have 2723 features, when I expect to have 1. >>>> >>>> What am I doing wrong? >>>> >>>> Roger >>>> _______________________________________________ >>>> 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
