PostGIS
See also working with external data in GRASS 7.
Help pages
- Database management in GRASS GIS help page
- SQL support in GRASS GIS help page
- PostgreSQL driver in GRASS help page
- ODBC driver in GRASS help page
Link to external dataset
- input maps: v.external
- (in GRASS 6 links are read only, for GRASS 7 see working with external data in GRASS 7)
- output maps: v.external.out (GRASS 7 only)
Import into GRASS
There is a fundamental difference between the PostGIS format which is non-topological and the internal GRASS format which is topological and which, thus, does not really allow for overlapping polygons. You can digitize them, but they are not really useful...
You cannot directly process a PostGIS table in GRASS. GRASS has its own internal vector format.
You can link a GRASS layer to a PostgreSQL attribute table, though. v.db.connect