PostGIS

PostGIS is an extension to the PostgreSQL object-relational database, which includes geographic objects and functions. PostgreSQL with PostGIS is a spatial database that can be integrated into geographic information systems. The project implements the Simple Feature Access specification of the Open Geospatial Consortium and supported by the Open Source Geospatial Foundation.

History

PostGIS is developed by Refractions Research since 2000. Although PostgreSQL itself already supported geometry types, these are not sufficient according to the developers to store and analyze spatial data can comprehensively. PostgreSQL provides the ability to define your own data types. These conditions were good to start the main motivation the development of a spatial extension for PostgreSQL.

The first version was released in May 2001 under the GNU General Public License and was numbered 0.1. This early version had the ability to load and query spatial objects, simple spatial functions, a spatial index for fast access to the data and a JDBC extension to connect to Java.

With version 0.5 PostGIS was supplemented format to the OpenGIS well-known binary and the names of existing features have been adapted to OpenGIS specifications.

In later versions, especially numerous spatial functions and operators have been added. Refractions Research began these functions in a standalone library called GEOS summarize, taking into account the OpenGIS specifications and a C port of JTS Topology Suite is. Since version 0.8, PostGIS uses the GEOS library.

The next developments were mainly towards a more efficient memory management. The new data structure called light-weight and geometry since version 1.0 is used exclusively this.

The current development of PostGIS into account enhances the ISO SQL / MM specification that more geometry types such as Curves implemented as the OpenGIS specification.

With version 2.0, the 9.1 has existed since PostgreSQL PostgreSQL Extensions system is being used.

Properties

PostGIS supports the following geometry types:

  • OpenGIS Well-Known Text and Well-Known Binary: Point, LineString, Polygon, Multipoint, Multiline String, Multi and GEOMETRYCOLLECTION
  • Extended Well-Known Text or Extended Well-Known Binary: extended OpenGIS Well-Known Text with a height information and / or with a measured value
  • SQL / MM ( not fully supported): CircularString, Compound Curve, Curve Polygon, MultiCurve MultiSurface

From PostGIS supported functions and operators:

  • Spatial functions such as calculating areas and distances, intersection, calculation of buffer zones, etc.
  • Spatial operators, such as Overlaps, Within, Contains, etc.
  • Functions for creating geometry
  • Analysis of raster and vector data
  • Functions for querying geometries in formats Well-Known Text, Well-Known Binary, GML, SVG, KML
  • Spatial indexing with GiST index

Access to geometry data

Accessing PostGIS is done with the same tools as the PostgreSQL databases. Examples of open source programs for database management are psql or pgAdmin. All existing PostgreSQL interfaces to various programming languages ​​can be used to access PostGIS databases also like a Java / JDBC connection or the C library libpq.

A number of GIS programs or libraries support PostGIS natively, such as GeoTools, MapServer, QGIS or GDAL / OGR.

There are also pgsql2shp and shp2pgsql the command -line utilities, which are used to convert ESRI shapefiles to PostGIS tables and placed upside down. Also can be imported using osm2pgsql OpenStreetMap data.

Extensions

WKT raster

WKT Raster is an extension to support raster data in PostGIS. An essential feature of this extension is the introduction of a raster data type similar to the existing geometry data type.

Route planning

With the module pgRouting PostGIS database functionality can be added to the route planning. PgRouting allows the creation of topologies and solving the following problems:

  • Shortest Path by Dijkstra's algorithm
  • Shortest path to A * algorithm
  • Shortest path algorithm by Shooting Star
  • Problem of the traveling salesman
  • Calculation of Isodistanzen from the edge topology
  • Route optimization for vehicle fleets
Java Database Connectivity Geography Markup Language Keyhole Markup Language A* search algorithm Deegree GeoServer OpenLayers
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