[FWTools] gdal_merge output file size

Frank Warmerdam warmerdam at pobox.com
Fri Aug 22 11:59:36 EDT 2008

Adam Yesaitis wrote:
> Hello friends,
>     I am new to Gdal so please excuse me if my questions are a bit basic.
>     I am currently using FWtools version 2.2.1.  My attempt is to mosaic 
> large amounts of .tif files using gdal_merge.  I have done this 
> successfully using gdal_merge to mosaic and compress the file into and 
> lzw or packbits compression.... I then further compress the files into 
> G4 compression, using gdal_translate, in order to yield reasonable file 
> sizes... between 9 and 20 MB preferably for larger datasets. 
>      When I use this process with smaller sets of images(7MB over 30 
> files)  the output files come out fine.  However when I move to larger 
> datasets (13MB over 150 files) the ouptut is corrupted and will not open. 
>     I would appreciate any suggestions to help me limit output file size 
> ( as when i mosaic the larger datasets the uncompressed output is well 
> over a gig per map) to the smallest it can possibly be.  Even when I 
> merge large datasets using G4 compression alone the output files are 
> over 100MB.


I can't think of any obvious reason that things would complete successfully
but produce corrupt files.  You are pretty confident that there are no
error messages during the processing?

Best regards,
I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | Geospatial Programmer for Rent

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