[gdal-dev] Gdalwarp with geolocation Array and nodata value

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[gdal-dev] Gdalwarp with geolocation Array and nodata value

Andre Joost
Dear list,

as a follow-up to
https://gis.stackexchange.com/questions/319147/using-gdalwarp-for-reprojecting-netcdf-file 
with a sample netcdf file linked in the comments:

The netcdf (really HDF5) contains lat and lon bands to reference the
cells to WGS84 coordinates. Unfortunately, some rows contain nodata
values for the monitored parameters and the lat-lon coordinates. This
seems to break gdalwarp -geoloc.

My workaround is to create a vrt file for the requested subdataset,
manually remove the GCP points with nodata values, and gdalwarp without
the -geoloc option (i.e. use the remaining GCPs).

Is there a config option for GDALwarp to omit those nodata values in the
geolocation array? Or is it worth to open a ticket for it?


Greetings,
Andre Joost

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Re: Gdalwarp with geolocation Array and nodata value

Even Rouault-2
On lundi 22 avril 2019 08:43:30 CEST Andre Joost wrote:

> Dear list,
>
> as a follow-up to
> https://gis.stackexchange.com/questions/319147/using-gdalwarp-for-reprojecti
> ng-netcdf-file with a sample netcdf file linked in the comments:
>
> The netcdf (really HDF5) contains lat and lon bands to reference the
> cells to WGS84 coordinates. Unfortunately, some rows contain nodata
> values for the monitored parameters and the lat-lon coordinates. This
> seems to break gdalwarp -geoloc.
>
> My workaround is to create a vrt file for the requested subdataset,
> manually remove the GCP points with nodata values, and gdalwarp without
> the -geoloc option (i.e. use the remaining GCPs).
>
> Is there a config option for GDALwarp to omit those nodata values in the
> geolocation array? Or is it worth to open a ticket for it?

Andre,

This was addressed by https://github.com/OSGeo/gdal/issues/1451 for the HDF5
driver side of things.
I'm a bit confused by your mention of -geoloc, since the HDF5 driver has no
support for the GEOLOCATION metadata domain.
The netCDF driver does have support for GEOLOCATION, but for that particular
sample file, it doesn't manage to identify the geolocation array, because it
is in another netCDF group.
So it is likely that your -geoloc invokation ended up using GCPs

Even

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