PostGIS Topology: Difference between revisions
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*:For each centroid is defined by area within the centroid is located. | *:For each centroid is defined by area within the centroid is located. | ||
* ''areas'' - topologically correct areal elements formed by closed set of boundaries and one centroid located inside the area | * ''areas'' - topologically correct areal elements formed by closed set of boundaries and one centroid located inside the area | ||
*:For each area is defined by list of boundaries which forms the area (outter ring), | *:For each area is defined by list of boundaries which forms the area (outter ring), and by list of isles 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) | * ''isle'' - inner ring (closed set of boundaries) located inside area (note that inner ring is not allowed to touch the area boundary) | ||
*:For each isle is defined by list of boundaries which forms the isle (it's outter ring) and area | *:For each isle is defined by list of boundaries which forms the isle (it's outter ring), and by the area where the isle is located. | ||
For other info and examples see [http://grass.osgeo.org/programming7/vlibTopology.html programmer's manual]. | For other info and examples see [http://grass.osgeo.org/programming7/vlibTopology.html programmer's manual]. | ||
Revision as of 13:44, 29 November 2012
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 various topological elements:
- nodes - point elements
- For each node is defined which lines/boundaries starts and ends in this node.
- lines - linear elements which are not forming areas
- For each line is defined by start and end node.
- boundaries - linear elements which can form areas
- For each line is defined by start and end node, and by the area on the left and right.
- centroids - point located inside area
- For each centroid is defined by area within the centroid is located.
- areas - topologically correct areal elements formed by closed set of boundaries and one centroid located inside the area
- For each area is defined by list of boundaries which forms the area (outter ring), and by list of isles 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 each isle is defined by list of boundaries which forms the isle (it's outter ring), and by the area where the isle is located.
For other info and examples see programmer's manual.
PostGIS Topology Model
PostGIS Topology model is based on ISO standard 13249. The model defines only three topological elements:
- nodes - point elements
- edges - linear elements
- faces - area elements
See also
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)