Hi Matthias,
sorry for the late reply.
I think this is related to PixelIsCorner vs PixelIsCenter convention.
http://docs.geotools.org/stable/javadocs/org/geotools/geometry/GeneralEnvelope.html
In OGC, the grid to CRS transform maps the cell center.
I think that when using the evaluate method you should provide the cell's
center coordinates while GeneralEnvelope reports the cell's corner
coordinates.
(So there is an half pixel shift to be taken into account)
Something like this should work:
GridGeometry gridGeometry = gridCoverage.getGridGeometry();
MathTransform transform = gridGeometry.getGridToCRS();
// supposing you want to get a coverage's corner
DirectPosition2D sourceDp = new
DirectPosition2D(gridGeometry.getGridRange().getLow(0),
gridGeometry.getGridRange().getHigh(1));
DirectPosition2D targetDp = new DirectPosition2D();
transform.transform(sourceDp, targetDp);
gridCoverage.evaluate(targetDp);
Hope this helps.
Daniele
On Fri, Feb 8, 2019 at 2:19 PM Matthias Müller <
matthias_muel...@tu-dresden.de> wrote:
> I am trying to lookup 2D point values from a GeoTiff coverage an got the
> following error from /GridCoverage2D.evaluate()/ [1] (Geotools 20.2)
>
> From the GeoTiff's envelope I would assume that the point (0, -90) is
> within the valid extent but /GridCoverage2D.evaluate()/ seems to think
> otherwise. It the output of /GridCoverage2D.getEnvelope()/ consistent with
> the (minimal) bounding box of the coverage or must I use a different query
> to obtain the valid extent?
>
> Thanks,
> Matthias
>
> p.s.: I tested this with a few thousand other points, distributed
> world-wide. So the general procedure seems to work.
>
> [1]:
> GEOGCS["WGS 84",
> DATUM["World Geodetic System 1984",
> SPHEROID["WGS 84", 6378137.0, 298.257223563,
> AUTHORITY["EPSG","7030"]],
> AUTHORITY["EPSG","6326"]],
> PRIMEM["Greenwich", 0.0, AUTHORITY["EPSG","8901"]],
> UNIT["degree", 0.017453292519943295],
> AXIS["Geodetic longitude", EAST],
> AXIS["Geodetic latitude", NORTH],
> AUTHORITY["EPSG","4326"]]
> GeneralEnvelope[(-180.0, -90.00000000000001), (180.00000000000006, 90.0)]
>
> ...
>
> org.opengis.coverage.PointOutsideCoverageException: Coordinate (0, -90) is
> outside coverage.
>
> at
> org.geotools.coverage.grid.GridCoverage2D.evaluate(GridCoverage2D.java:454)
> at
> org.geotools.coverage.grid.GridCoverage2D.evaluate(GridCoverage2D.java:398)
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>
--
Regards,
Daniele Romagnoli
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