[GRASS-user] Ortho Photo mosaic

[Lisa Stillwell]

Hi. Does anyone know of a relatively quick method of joining together  
color ortho photo tiles to create 1 huge image. I need to join about  
2000 tiles into one image.
The individual images are 5000 rows x 5000 columns, and they are all  
already in the same projection. Is there any software available (free  
or not)  that can do this quickly (i.e. less that 1 week?) I have  
tried r.patch and mapcalc in grass, but that seems way too slow. I  
heard something about gdal_merge.py. Has anyone tried this? BTW - I  
would like to preserve the projection in the final image and be able  
to import it into grass.

thanks,
Lisa Stillwell