[gdal-dev] gdalwarp across the antimeridian with a source extent >180E

[Michael Sumner]

Thanks!   Educational as ever, this closes out a few hanging threads for
me, much appreciated.

Cheers, Mike



On Mon, Jun 3, 2024 at 3:48 AM Even Rouault <even.rouault at spatialys.com>
wrote:

> Michael,
>
> https://github.com/OSGeo/gdal/pull/10108 will fix it.
>
> You can also workaround the issue by overriding the extent of the source
> dataset to be exactly -179.995,89.995,180.005,-89.995 with
>
>
>  "vrt://NETCDF:20240102090000-JPL-L4_GHRSST-SSTfnd-MUR-GLOB-v02.0-fv04.1.nc:
> analysed_sst?a_srs=EPSG:4326&a_ullr=-179.995,89.995,180.005,-89.995"
>
> The issue was twofolds:
>
> - the dataset uses lon/lat arrays with single precision floating-point
> numbers. Hence -179.99 gets actually read a a   read as -179.99000549316406
> as a double-precision number, and thus the maxx - minxx difference was
> slightly over 360 degrees. I've added a heuristics to try to round
> -179.99-single-precision as -179.99-double-precision
>
> - which defeated a heuristics in the warper to identify the center
> longitude of a dataset registered in a geographic CRS. This center
> longitude is just (min_lon + max_lon) / 2 if the dataset doesn't cover more
> than 360 degrees of longitude. This value, when computed, is passed as a
> hint OGRCoordinateTransformation so that it can post-correct longitudes to
> apply a +/- 360 degree offset, to be in the range of the source dataset.
> I've relaxed the sanity check to allow slighly more than 360 degrees
>
> Even
>
>
> Le 01/06/2024 à 08:19, Michael Sumner via gdal-dev a écrit :
>
> This data source has an odd georeferencing, it's a 36000x17999 raster in
> the extent -179.995 -89.995 180.005 89.995.
>
> vrt://NETCDF:/vsicurl/
> https://archive.podaac.earthdata.nasa.gov/podaac-ops-cumulus-protected/MUR-JPL-L4-GLOB-v4.1/20240101090000-JPL-L4_GHRSST-SSTfnd-MUR-GLOB-v02.0-fv04.1.nc:analysed_sst?a_srs=EPSG:4326
>
> (Why is it 17999: well there's one missing row - you'd expect 18000 at
> 0.01 resolution and that manifests as half a cell short at the top and
> bottom).
>
> But also the x registration is half a cell to the east from what you would
> expect.
>
> It's correctly registered in that frame though, if we shift it west by the
> half cell I've verified visually that it "looks wrong" compared to
> coastlines etc.
>
> The point of this report is, gdalwarp misses the western window of data
> for a request across the antimeridian (there's no data in the output east
> of 180).
>
> gdalwarp $dsn -te 173.00 -19.85 185.00 -15.00 out1.tif -co COMPRESS=LZW
>
> If we "fix" the extent to be more longitudinally pleasing, we get the data
> east of the antimeridian, the map is properly filled either side of the
> antimeridian.
>
>
> vrt://NETCDF:/vsicurl/
> https://archive.podaac.earthdata.nasa.gov/podaac-ops-cumulus-protected/MUR-JPL-L4-GLOB-v4.1/20240101090000-JPL-L4_GHRSST-SSTfnd-MUR-GLOB-v02.0-fv04.1.nc:analysed_sst?a_srs=EPSG:4326&a_ullr=-180,89.995,180,-89.995
>
> gdalwarp $dsnfix -te 173.00 -19.85 185.00 -15.00 out2.tif -co COMPRESS=LZW
>
>
> Which is good, but as mentioned above the workaround means we are now half
> a cell out. It works fine for projected windows over the antimeridian in
> either situation.
>
> The compressed file sizes reflect the missing data in the second one,
> these are 625K and 1.1Mb.
>
> I'd like the warper to be able to correctly fill the data from the western
> window in the original case, we have determined that we can't feasibly
> "fix" the extent.
>
> Or maybe something else I'm missing? I don't *think* SAMPLE_GRID or
> SOURCE_EXTRA helps here. I know that I could craft a meridian-crossing
> combination in VRT but I'd rather like this workflow to work as-is.
> (Chasing down the weird grid referencing is another project, but it's a
> really massive dataset so I'm pretty unconfident of that occurring).
>
> Cheers, Mike
>
> --
> Michael Sumner
> Research Software Engineer
> Australian Antarctic Division
> Hobart, Australia
> e-mail: mdsumner at gmail.com
>
> _______________________________________________
> gdal-dev mailing listgdal-dev at lists.osgeo.orghttps://lists.osgeo.org/mailman/listinfo/gdal-dev
>
> -- http://www.spatialys.com
> My software is free, but my time generally not.
>
>

-- 
Michael Sumner
Research Software Engineer
Australian Antarctic Division
Hobart, Australia
e-mail: mdsumner at gmail.com
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