[gdal-dev] GTiff optimisation

Yves Jacolin yjacolin at free.fr
Thu Sep 1 05:29:07 EDT 2011


Le jeudi 01 septembre 2011 10:39:50, Yves Jacolin a écrit :
> Le mercredi 31 août 2011 16:45:09, Jean-Claude Repetto a écrit :
> > Le 31/08/2011 14:13, Yves Jacolin a écrit :
> > > Another question: I have 2 000 ECW files (40 Mo each), 49 ECW files (1
> > > Go each) and 2 ECW files (2 Go each). I worked first on 2 Go ECW file,
> > > it takes around 1 day to assign the projection information in the
> > > files.
> > > 
> > > Do you think this is normal? How can I improve this?
> > 
> > Since you are using Linux, you may be interested in a tool I wrote a few
> > years ago :
> > http://jrepetto.free.fr/ecwhed/
> > 
> > You can compile it manually by a command such as :
> > g++ -o ecwhed -l pthread  ecwhed.cpp /usr/lib64/libecwj2.a
> > 
> > ( The standard procedure ./configure; make; make install is not working
> > anymore. If you know the autotools, may be you can fix it).
> > 
> > Jean-Claude
> 
> Thanks Jean-Claude for your reply as I could build your app. Here some
> feedback:
> 
> * original data show correct header with projection information
> 
> * data made from gdal show "raw" as DATUM and PROJ using ecwhed utilities:
> >Datum = RAW
> >Projection = RAW
> 
> What I don't understand is that QGIS or GDAL don't find it from the
> original data. Is it possible that there is some ECW specific projection
> information as ESRI one? I saw an ecw_cs.wkt file in the gdal data dir.
> 
> Any idea?
> 
> Thanks,
> 
> Y.
I know why raster data made by GDAL show "RAW" string as projection 
information, documentation explain it:
> When writing coordinate system information to ECW files, many less common 
> coordinate systems are not mapped properly. If you know the ECW name for the 
> coordinate system you can force it to be set at creation time with the PROJ 
> and DATUM creation options.

As I did not use DATUM and PROJ creation option GDAL don't add it!

Finally I saw that gdal create only an aux.xml file to store his own proj 
information and don't use the projection information from the header file. If I 
create this aux.xml file for all of my raster data it could work.

Thanks again for your help.

Y.
-- 
Yves Jacolin

http://yjacolin.gloobe.org


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