OK, so this is what I have found so far:
1) To obtain the correct raster projection from NZMG to NZTM I need to set
the system property and NOT use the OGC URN code
Here's my code snippet:
<pre>
System.setProperty("org.geotools.referencing.forceXY", "true");
File[] filesin = new File[1];
filesin[0] = new File("TestData/heathcote_200_depth.png");
File[] filesout = new File[1];
filesout[0] = new File("TestData/NZTM/heathcote_200_depth.png");
int i = 0;
for (File rasterFile : filesin) {
WorldImageReader reader = new WorldImageReader(rasterFile, null);
GridCoverage2D myGridCov = reader.read(null);
GridCoverage2D reprojected = (GridCoverage2D)
Operations.DEFAULT.resample(myGridCov, CRS.decode("EPSG:2193"), null,
null);
WorldImageWriter wiw = new WorldImageWriter(filesout[i], null);
ParameterValueGroup params = reader.getFormat().getWriteParameters();
params.parameter(WorldImageFormat.FORMAT.getName().toString()).setValue("png");
GeneralParameterValue[] gpv = {
params.parameter(WorldImageFormat.FORMAT.getName().toString()) };
wiw.write(reprojected, gpv);
wiw.dispose();
i++;
}
</pre>
2) There is no problem at all to reproject a ReferencedEnvelope from NZMG to
NZTM
<pre>
CoordinateReferenceSystem sourceCRS = CRS.decode("EPSG:27200");
ReferencedEnvelope envelope = new ReferencedEnvelope(2823200.0, 2848750.0,
6157410.0, 6174960.0, sourceCRS);
CoordinateReferenceSystem targetCRS = CRS.decode("EPSG:2193");
ReferencedEnvelope newEnv = envelope.transform(targetCRS, false);
</pre>
Yealds a bounding box of
1913218.3251509198
1938797.0025404787
5595756.03690457
5613329.706339548
All's good here
3) *There is a problem reprojecting the ReferencedEnvelope from NZTM to
NZMG.*
The ReferencedEnvelope reprojection consistently gives the wrong answers,
whether I use the system setting, OSG URN or various combinations of the
above.
You can see for yourself by trying
<pre>
CoordinateReferenceSystem sourceCRS =
CRS.decode("urn:ogc:def:crs:EPSG::2193");
ReferencedEnvelope envelope = new ReferencedEnvelope(1567451.39, 1570650.34,
5178586.92, 5184734.56, sourceCRS);
CoordinateReferenceSystem targetCRS =
CRS.decode("urn:ogc:def:crs:EPSG::27200");
ReferencedEnvelope newEnv = envelope.transform(targetCRS, false);
System.out.println(newEnv.getMinX());
System.out.println(newEnv.getMaxX());
System.out.println(newEnv.getMinY());
System.out.println(newEnv.getMaxY());
</pre>
The only way I can get this to work is by manually swapping x and y
coordinates :-(
ReferencedEnvelope envelope = new ReferencedEnvelope(5178586.92, 5184734.56,
1567451.39, 1570650.34, sourceCRS);
This, as discussed previously, is not a acceptable solution.
4) Raster reprojection from NZTM to NZMG works OK for the code as above
(with EPSG codes reversed)
So it seems to me, that there is a bug somewhere in the ReferencedEnvelope
reprojection.
How to proceed?
Gaby
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