PostGIS Topology

PostGIS Topology allows to store topological vector data in PostGIS database. It's available in PostGIS 2.0 and greater. GRASS supports PostGIS Topology in version GRASS 7.0 and greater through GRASS-PostGIS data provider.

Background

Topological models used by GRASS and PostGIS Topology are different - see bellow.

GRASS Topology Model

In GRASS model are defined different topological elements:

• nodes
• lines - linear elements defined by start and end node which are not forming areas
• boundaries' - linear elements defined by start and end node which can form areas
• centroids' - point located inside area
• areas - topologically correct areal elements formed by closed set of boundaries and one centroid located inside the area
• isle - inner ring (closed set of boundaries) located inside area (note that inner ring is not allowed to touch the area boundary)

For other info and examples see programmer's manual.

See also

• Working with external data in GRASS 7
• PostGIS

External links

• PostGIS Topology manual
• PostGIS Topology wiki page
• State of the art of FOSS4G for topology and network analysis (FOSS4G 2010)
• strk's page about PostGIS
• PostGIS topology ISO SQL/MM complete (strk's blog)
• Simplifying a map layer using PostGIS topology (strk's blog)
• Topo-Geo-and-Topo-Net - The Concepts • Routine Details
• ISO 13249-3 Information Technology - Database languages - SQL Multimedia and application packages (Text for FDIS)