Coordinate Transformation Service
What a Coordinate Reference System is ?
Coordinate Reference Systems are of 3 main sorts : - Cartesian (not much used except by geodesian and during transformation processes) - Geographic (longitude, latitude, and sometimes elevation or height above ellipsoid) - Projected (used for cartographic purposes, there are dozens of possible projection)
Coordinate Reference System are mainly defined by - A Datum (WGS84, ETRS, ED50...) : mandatory for any CRS - An Ellipsoid : mandatory for Geographic and Projected CRS - A Prime Meridian : mandatory for Geographic and Projected CRS - A projection : mandatory for Projected CRS
There is a well established CRS database called EPSG, including definition of hundreds of CRS.
Coordinate Transformation Service
There is popular and mature CRS transformation tool called [Proj4 http://trac.osgeo.org/proj/] which is used by - PostGIS (spatial database) - OGR2OGR (a popular command line tool able to change coordinates and/or data format of a dataset)
Coordinate Transformation Service in/from Java
GeoAPI It is a library including java interfaces conforming OGC Standards for Coordinate Transformation Service and some other topics. At the origin, it has been developped to make libraries like OpenJUMP and Geotools interoperable. Today, GeoToolKit is the only java library implementing the GeoAPI, but adapters have been developed for Proj4 to prove GeoAPI can be a general interface for any CTS implementation.
GeoTools and GeoToolKit GeoTools has developped a pure java Coordinate Transformation Service. It has been a GeoAPI implementation for a long time, but it is no more. Ede has developped a [OpenJUMP PlugIn] which makes GeoTools CTS accessible from OpenJUMP. It is based on a quite old version of GeoTools. GeoToolKit is a fork of GeoTools. GeoToolKit is still a strict implementation of GeoAPI. JhLabs has ported Proj4 code into Java. It is not a complete implementation of GeoAPI and has much less classes than GeoTools or GeoToolKit. It is available from two places : - As Proj4J, on tutsiat website, the site of M. Davis who is maintaining the code - As JMapProjLib, on sourceforge, maintained by B. Jenny
IGOR ISA has developped a thin wrapper making OGR2OGR available from java (and from SkyJUMP). It is Mainly a java UI calling OGR2OGR.exe SkyJUMP com/isa/jump/plugin/igor package contains 4 classes which may be able to port IGOR to OpenJUMP quite easily.
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