[gdal-dev] gdalwarp swath satellite data issue using gdal1.6.0

[Simona Oancea]

Dear List,



I would like to reproject METOP SST data (satellite data which are swath
data granules stored in the netcdf file) with GDAL geolocation arrays.

I have run the followings commands using Gdal 1.6.0:



1. Here I extract the subsetdata. The same command is used for latitude and
longitude data

gdal_translate -a_srs EPSG:4326 -a_ullr ${granule[@]} -of GTiff -co
"compress=lzw" ${inputdata} ${outputdata}

2. build VRT file for every data subset extracted  (SST , lat and lon)
using a command like that:

gdalbuildvrt ${fileSSTVrt} ${fileSSTRawData}

3.Then reproject the SST raw data

gdalwarp -t_srs '+proj=latlong +datum=WGS84' -te ${te_arg_granule[@]} -tr
${ps} ${ps} -srcnodata ${nodataValue} -dstnodata ${nodataValue} -r near -of
GTiff -co "compress=lzw" -geoloc ${fileSSTVrt} ${fileSSTReproject}

 The geolocation arrays have the same size as the raw data (SST data).

Using geolocation arrays it seems to work well but we found the resulting
image quality not so good when we compare it with one obtained  by using
ENVI option, Georeference from INPUT geometry with the same method of
resampling: nearest neighbor.



I’m wondering if this might be due to the gdal version which we used it
(1.6.0) and that is improved in the later version of gdal software or it is
something wrong in the way I used the commands mentioned above.



Please, if someone has experienced the same problem, I would like to know
how he/she did to improve the results.



Thank you in advance

Simona



Joint Research Centre of the European Commission
MONDE Action - GEM/IES
v. E. Fermi 2749, 21020 Ispra (VA) - Italy
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