Added by jgarnett, last edited by jgarnett on Apr 01, 2008  (view change)

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Contains implementations of Coordinate Reference Systems (CRS), conversion and transformation services.

This module is basically care and feeding for the CoordinateReferenceSystem class - and enough math to make it useful. Before you get too worried it is easy to use (There is a class called CRS that has helper methods for reprojection and stuff).

Before you start - choose only one epsg jar

The referencing module does not do very much out of the box - it needs someone to tell it what all the funny codes mean (such as "EPSG:4326").

You need to choose a single epsg jar to have on your classpath; if you have several epsg jars on your classpath you will get a FactoryException.

For most needs just use the epsg-hsql plugin:

  • EPSG HSQL Plugin: will unpack an hsql database containing the official epsg database into a temp directory, a great solution for desktop applications.

There are several alternatives:

  • EPSG WKT Plugin: uses an internal property file and is lightweight rather than official and correct. A great solution for applets
  • EPSG Postgres Plugin: uses the official epsg database which you have to load into PostgreSQL yourself. A great solution for Java EE applications.
  • EPSG Access Plugin: directly use an the official epsg database as distributed. A great solution for windows users.
  • EPSG Oracle Plugin: currently unsupported

The main module includes definitions of AUTO and AUTO2 and several other OGC inspired ideas.
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What Jars do I need?

As an example to use epsg-hsql you will need:

C:\geotools\trunk\modules\plugin\epsg-hsql>mvn dependency:tree
...
------------------------------------------------------------------------
Building EPSG Authority Service using HSQL database
   task-segment: [dependency:tree]
------------------------------------------------------------------------
[dependency:tree]
org.geotools:gt2-epsg-hsql:jar:2.5-SNAPSHOT
+- junit:junit:jar:3.8.1:test
+- javax.media:jai_core:jar:1.1.3:provided
+- org.geotools:gt2-referencing:jar:2.5-SNAPSHOT:compile
|  +- java3d:vecmath:jar:1.3.1:compile
|  +- commons-pool:commons-pool:jar:1.3:compile
|  \- org.geotools:gt2-metadata:jar:2.5-SNAPSHOT:compile
|     +- org.opengis:geoapi:jar:2.2-SNAPSHOT:compile
|     +- javax.units:jsr108:jar:0.01:compile
|     \- edu.oswego:concurrent:jar:1.3.4:compile
+- org.geotools:gt2-sample-data:jar:2.5-SNAPSHOT:test
+- hsqldb:hsqldb:jar:1.8.0.7:compile
+- net.sourceforge.groboutils:groboutils-core:jar:5:test
\- commons-dbcp:commons-dbcp:jar:1.2.2:test
------------------------------------------------------------------------

Limitations

GeoTools performs datum shift using Bursa-Wolf parameters at this time. The rare case of a Datum shift backed by grids are only partially implemented.

Rueben Shulz has implemented data shift backed by grids for NADCON with the following limitations:

  • Use of NADCON grids has not been intergrated with DefaultCoordinateOperationFactory (so you would need to set it up by hand)
  • The general case of a Datum shift provided by a grid is not covered, for example Spanish Datum Changes ED50-ETRS89 will not work

Talk to the module maintainer (Martin Desruisseux) if you have funding for this very important work.