Coordinate transform

Question

Do any open source or 'free' libraries exist for Java where i can perform coordinate transforms from one spatial system to another?

I found Opengeo http://opengeo.org/ but it's a huge and comprehensive library for all sorts of spatial things.

Does anything smaller exist? I need to convert from MGA56 to WGS84.

What transformation do you need (from what to what)? – Seth Nov 04 '09 at 23:55 — Seth, Nov 04 '09 at 23:55

score 4 · Answer 1 · answered Dec 11 '13 at 13:43

There is a lightweight library written fully in Java.

Coordinate Transformation Suite (abridged CTS) is a library developed to perform coordinate transformations using well known geodetic algorithms and parameter sets.

CTS handles 4257 coordinate reference systems (3910 EPSG).

The source code of this project is located at:

https://github.com/irstv/CTS

Daniel Pryden · Accepted Answer · 2009-11-05T02:29:33.230

3

A simple solution is PROJ.4, but it doesn't have Java bindings, so working with it might be a bit tricky. A more complete (but probably bigger than you want) solution would be GeoTools. But a quick search found the Java Map Projection Library, which appears to be a Java port of PROJ.4. I would give that a try.

Since it appears you need to do a datum shift, not only a projection, you will need to have some kind of coordinate system database. The easiest to get a hold of is the EPSG database -- PROJ.4 comes with an EPSG mapping file, which should be good enough for most purposes.

It looks like MGA56 is EPSG:28356, and of course WGS84 is EPSG:4326.

edited Nov 05 '09 at 02:29

answered Nov 05 '09 at 02:24

Daniel Pryden

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OP appears to be already using GeoTools: http://stackoverflow.com/questions/1676940/google-maps-spatial-reference-system – Greg Hewgill Nov 05 '09 at 02:31
PROJ.4 looks great. i used ProjectionFactory.getNamedPROJ4CoordinateSystem() to grab the projections. But no transform is possible. I read the docs it says "Coordinate system and geodetic datum conversion is missing. " – JavaRocky Nov 05 '09 at 03:21
If you're using GeoTools, don't bother with working with PROJ4 directly -- use `CRSAuthorityFatory.createCoordinateReferenceSystem(epsgString)`, for EPSG strings `"EPSG:28356"` and `"EPSG:4326"` and then do `CRS.findMathTransform(sourceCRS, targetCRS, true)`. You will need to have one of the GeoTools EPSG JARs on your classpath -- I would recommend `gt-epsg-hsql`, which is the easiest to work with. – Daniel Pryden Nov 06 '09 at 18:08

score 2 · Answer 3 · edited Jun 20 '20 at 09:12

I've needed to convert back and forwards between WGS84 (the GPS projection) and EPSG 27700 (UK National Grid) and I've found the geotrellis library most accurate and usable. It's written in Scala but obviously you can use the library in Java. Here's the maven dependency I've used:

        <dependency>
            <groupId>org.locationtech.geotrellis</groupId>
            <artifactId>geotrellis-proj4_2.12</artifactId>
            <version>2.3.1</version>
        </dependency>

and this is some example code:

       CRS epsg27700 = CRS.fromEpsgCode(27700);
        CRS wgs84 = CRS.fromEpsgCode(4326);

        var toWgs84 = Transform.apply(epsg27700, wgs84);
        var fromWgs84 = Transform.apply(wgs84, epsg27700);

        Tuple2<Object, Object> southWestInWgs84 = toWgs84.apply(-90_619.29, 10_097.13);
        System.out.println("South-West corner in WGS 84: " + southWestInWgs84._1() + "," + southWestInWgs84._2());
        Tuple2<Object, Object> southWestBackToEpsg27700 = fromWgs84.apply(southWestInWgs84._1(), southWestInWgs84._2());
        System.out.println("South-West corner back to EPSG 27700: " + southWestBackToEpsg27700._1() + "," + southWestBackToEpsg27700._2());

which produces this output:

South-West corner in WGS 84: -8.820000046234389,49.7899999643445

South-West corner back to EPSG 27700: -90619.2888566542,10097.128186725415

Coordinate transform

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