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Vector maps can be imported from various sources such as ArcInfo-Coverages, CSV, DGN, SHAPE files, GML, MapInfo, MySQL, ODBC, OGDI, PostgreSQL/PostGIS, S57, SDTS, TIGER, UK .NTF, and VRT. The module for importing vector maps is v.in.ogr. The input ``dsn'' (data source name) parameter can be a file, a directory or a database connection, depending on the data format. As GRASS is a topological GIS, non-topological Simple Feature data such as SHAPE files are transformed into a topological representation upon import. Data quality is verified during the import, and vector features which violate topological conditions are stored in a separate layer for later inspection. For more details please refer to the manual page of v.in.ogr.
As an example, we import a SHAPE file map generated from TIGER 2000
data into the Spearfish location and look at it:
v.in.ogr dsn=tiger_lines.shp out=tiger_lines
d.vect tiger_lines
Maps can also be simply registered using v.external. In this case only pseudo-topology is generated and the map is read-only (so no modifications can be done).