[geotk] Re: Building a GeographicCRS from scratch

[Pablo Rozas Larraondo]

Sorry I made a mistake repeating the x coordinate on the Geotoolkit code.
The correct output is:

BOX2D(-704.9721645900614, -584.9804882997278, 705.0278354099386,
585.0195117002722)


Hello,
>
> I'm working with a Grib file that uses a Lambert Conformal Conic
> projection. This projection doesn't correspond to any registered EPSG code
> but all the information about the projection is in the descriptor of the
> grib file using the standard WMO format (
> http://dss.ucar.edu/docs/formats/grib/gribdoc/lcgrid.html).
>
> I suspect that the NetCDF API is capable of processing some of this data
> but not all of it. (latitudeOfFirstPointInDegrees doesn't match with the
> one I get with NetCDF...)
>
> To solve this issue I'm thinking in using the Geotoolkit API and creating
> a GeographicCRS and Conversion objects from scratch to project my file in
> cartesian coordinates. There are a lot of attributes in the Grib descriptor
> as: uvRelativeToGrid, LoVinDegrees, earthIsOblate, etc. that I somehow have
> to translate into parameters of this objects, but I not sure about how to
> do it... Does anyone has experience in doing a similar task?
>
>
> Another issue I've found working with my file is the difference between
> the NetCDF and the GeoToolkit API when they read the extreme values of the
> x&y axis values. The difference is small but significant, is this normal?
>
> I paste the code I've used and the output I got:
>
> CODE NETCDF API:
> NetcdfDataset ds = NetcdfDataset.openDataset("~/myfile.grb");
> CoordinateAxis xAxis = ds.findCoordinateAxis("x");
> CoordinateAxis yAxis = ds.findCoordinateAxis("x");
> System.out.println("BOX2D("+yAxis.getMinValue()+",
> "+xAxis.getMinValue()+", "+yAxis.getMaxValue()+",
> "+xAxis.getMaxValue()+")");
>
> OUTPUT:
> BOX2D(-704.9721645900614, -704.9721645900614, 705.0278354099386,
> 705.0278354099386)
>
>
> CODE GEOTOOLS API:
> NetcdfImageReader netcdfReader = new NetcdfImageReader(null);
> netcdfReader.setInput("~/myfile.grb");
>
> ImageCoverageReader reader = new ImageCoverageReader();
> reader.setInput(netcdfReader);
>
> GridCoverage2D coverage = reader.read(0, null);
> reader.dispose();
> netcdfReader.dispose();
>
> System.out.println(coverage.toString());
>
> OUTPUT:
> GridCoverage2D["Precipitation_rate", BOX4D(-706.2221645900614
> -586.2304882997278 NaN NaN, 706.2778354099386 586.2695117002722 NaN NaN),
> NetcdfCRS.Compound["time height_above_ground3 y x"]]
> │   RenderedSampleDimension("Precipitation_rate":[])
> │       GeophysicsCategory(“No data”:[NaN(-9999…-9999)])
> └ Image=WritableRenderedImageAdapter[] as views [NATIVE, PACKED, RENDERED,
> GEOPHYSICS, PHOTOGRAPHIC]
>
> Cheers!
>
> Pablo Rozas
>
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