Gdalwarp producing odd results around 0 degree longitude

[simonrp84]

Hello,

I am warping ECMWF grib data (full globe, 0.25 degree resolution) to
match the SEVIRI geostationary satellite projection. I use this command:

gdalwarp -overwrite -ot Float32 -t_srs "+proj=geos +a=6378169
+b=6356583.8 +lon_0=0.0 +h=35785831" -te -5570248.832537 5570244.832537
5567248.429179 -5567252.429179 -ts 3712 3712 -wo NUM_THREADS=6 -wo
SOURCE_EXTRA=1000 -q -r cubicspline --config CENTER_LONG 180
/data/ECMWF_T2_20181223T00_000.grib /data/cubicspline.tiff

The output projection looks good, and if I try this with the ECMWF
land-sea mask then I can see that it is correct for most of the view.
However, along a vertical centred on zero degrees longitude I see this
artefact: https://i.stack.imgur.com/tQn5F.png

Any ideas what is causing that, and how to resolve this bug? The artefact
appears for all resampling methods except nearest neighbour.

Thanks,
Simon

[rouault]

Can you point to a source dataset that can be used to reproduce the issue ?

[simonrp84]

Apologies for the delayed reply. You can find an example dataset here:
https://github.com/simonrp84/temp_bugreport_data/blob/master/ECMWF_CAPE_20190121T12_000.grib

I tested this with:
gdalwarp -overwrite -ot Float32 -t_srs "+proj=geos +a=6378169 +b=6356583.8 +lon_0=0.0 +h=35785831" -te -5570248.832537 5570244.832537 5567248.429179 -5567252.429179 -ts 3712 3712 -wo NUM_THREADS=6 -wo SOURCE_EXTRA=1000 -q -r cubicspline --config CENTER_LONG 180 /data/ECMWF_CAPE_20190121T12_000.grib /data/cubicspline.tiff

I also tried several other CENTER_LONG values, and omitting the parameter entirely.

[simonrp84]

Is there any update on this?

[rouault]

I managed to reproduce the issue. The fundamental problem is that the resampling kernel is not geography aware, so when interpolating around longitude = 0 or 360 in your source raster, it is has the edge of the raster and fallback to nearest resampling.
A workaround is to "shift" your raster in the more usual [-180,180] range

gdal_translate ECMWF_CAPE_20190121T12_000.grib left.vrt -a_ullr -360.125 90.125 -0.125 -90.125 -of VRT
gdalbuildvrt in.vrt left.vrt ECMWF_CAPE_20190121T12_000.grib
gdal_translate in.vrt in_shifted.vrt -projwin -180.125 90.125 180.125 -90.125 -of VRT
gdalwarp -overwrite -ot Float32 -t_srs "+proj=geos +a=6378169 +b=6356583.8 +lon_0=0.0 +h=35785831" -te -5570248.832537 5570244.832537 5567248.429179 -5567252.429179 -ts 3712 3712 -wo NUM_THREADS=6 -wo SOURCE_EXTRA=1000  -r cubicspline in_shifted.vrt  out.tif