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<p class=""><span style="font-size:10pt;font-family:"Arial","sans-serif"">Dear
List,</span></p>

<p class=""><span style="font-size:10pt;font-family:"Arial","sans-serif""> </span></p>

<p class=""><span style="font-size:10pt;font-family:"Arial","sans-serif"">I
would like to reproject METOP SST data (satellite data which are swath data
granules stored in the netcdf file) with GDAL geolocation arrays.</span></p>

<p class=""><span style="font-size:10pt;font-family:"Arial","sans-serif"">I
have run the followings commands using Gdal 1.6.0:</span></p>

<p class=""><span style="font-size:10pt;font-family:"Arial","sans-serif""> </span></p>

<p class=""><span style="font-size:10pt;font-family:"Arial","sans-serif"">1.
Here I extract the subsetdata. The same command is used for latitude and
longitude data</span></p>

<p class=""><span style="font-size:10pt;font-family:"Arial","sans-serif"">gdal_translate
-a_srs EPSG:4326 -a_ullr ${granule[@]} -of GTiff -co "compress=lzw"
${inputdata} ${outputdata}</span></p>

<p class=""><span style="font-size:10pt;font-family:"Arial","sans-serif"">2.
build VRT file for every data subset extracted  (SST , lat and lon) using
a command like that:</span></p>

<p class=""><span style="font-size:10pt;font-family:"Arial","sans-serif"">gdalbuildvrt
${fileSSTVrt} ${fileSSTRawData}</span></p>

<p class=""><span style="font-size:10pt;font-family:"Arial","sans-serif"">3.Then
reproject the SST raw data</span></p>

<p class=""><span style="font-size:10pt;font-family:"Arial","sans-serif"">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}</span></p>





<p class=""><span style="font-size:10pt;font-family:"Arial","sans-serif""> The
geolocation arrays have the same size as the raw data (SST data).</span></p>

<p class=""><span style="font-size:10pt;font-family:"Arial","sans-serif"">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.</span></p>

<p class=""><span style="font-size:10pt;font-family:"Arial","sans-serif""> </span></p>

<p class=""><span style="font-size:10pt;font-family:"Arial","sans-serif"">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.</span></p>

<p class=""><span style="font-size:10pt;font-family:"Arial","sans-serif""> </span></p>

<p class=""><span style="font-size:10pt;font-family:"Arial","sans-serif"">Please,
if someone has experienced the same problem, I would like to know how he/she
did to improve the results.</span></p>

<p class=""><span style="font-size:10pt;font-family:"Arial","sans-serif""> </span></p>

<p class=""><span style="font-size:10pt;font-family:"Arial","sans-serif"">Thank
you in advance </span></p>

<p class=""><span style="font-size:10pt;font-family:"Arial","sans-serif"">Simona</span></p>

<p class=""><span style="font-size:10pt;font-family:"Arial","sans-serif""> </span></p>

<p class="" style="margin-bottom:12pt"><span style="font-size:10pt;font-family:"Arial","sans-serif"">Joint Research Centre of the European
Commission<br>
MONDE Action - GEM/IES<br>
v. E. Fermi 2749, 21020 Ispra (VA) - Italy<br>
+39.0332.785548</span></p>

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