[gdal-dev] Strange effect in gdalwarp output

Monobakht nobakht.mo at gmail.com
Wed Jul 22 05:48:12 PDT 2015


Thank you Even for your reply. I am actually not a professional gdal user,
but looking at the thread that you posted I think the problem here is
slightly different. Georegistration accuracy of gdalwarp result is perfectly
fine, even better that MCTK result, and the bowtie effect is not present.
I think it is a problem in resampling step that causes this artefact! Is
that what you meant?

Regards
Mohamad


Even Rouault-2 wrote
> Monobakht,
> 
> Probably due to the bow-tie effect of the MODIS scanning sensor. gdalwarp
> cannot currently deal with that correctly.
> 
> Discussed recently in this thread:
> http://osgeo-org.1560.x6.nabble.com/gdal-dev-gdalwarp-problems-with-MODIS-L1B-td5206583.html
> 
> Best regards,
> 
> Even
> 
>> This question was posted originally at
>> http://gis.stackexchange.com/questions/154959/strange-effect-in-gdalwarp-ou
>> tput
>> <http://gis.stackexchange.com/questions/154959/strange-effect-in-gdalwarp-
> > output> but I did not get any helpful response. Here is the problem:
>> 
>> I am using gdalwarp in python to extract and re-project reflectance bands
>> from MODIS level 1B (MOD021km). The command that I am using is the
>> following:
>> 
>> /
>> gdalwarp -of GTIFF -tps -t_srs EPSG:4326 -tr 0.01 0.01 -r bilinear
>> -overwrite
>> HDF4_EOS:EOS_SWATH:"C:\tmp\MYD021KM.A2007094.0935.006.2012075055042.hdf":MO
>> DIS_SWATH_Type_L1B:EV_500_Aggr1km_RefSB C:\tmp\Output.tif
>> /
>> 
>> It converts the hdf subdataset without any problem but the output file
>> seems to have some sort of artifact, specially close to the edges. (See
>> below)
>> <http://osgeo-org.1560.x6.nabble.com/file/n5216470/gdalwarp.jpg>
>> 
>> I converted the same data using Modis Conversion Toolkit (MCTK) and it
>> seems to be much better. (Below)
>> <http://osgeo-org.1560.x6.nabble.com/file/n5216470/MCTK.jpg>
>> 
>> I tried different resampling method and different output projection but
>> still the same results! Is there anyone having this issue with gdalwarp?
>> 
>> P.S. The data can be downloaded from this address:
>> ftp://ladsweb.nascom.nasa.gov/allData/6/MYD021KM/2007/094/MYD021KM.A2007094
>> .0935.006.2012075055042.hdf
>> 
>> 
>> 
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