[Gdal-dev] gdal_merge vs. gdalwarp

[Frank Warmerdam]

John Mitchell wrote:
> Hi,
> 
> I have found in comparing the speed between gdal_merge and gdalwarp that 
> gdal_merge mosaics tiles together more than twice as fast.  If all I 
> need to do is mosaic tiles together that are the same resolution and 
> keeping the same projection, then what advantage is using gdalwarp?  
> Also I noticed what I think is a new utility on the gdal utilities page 
> called " nearblack <http://www.gdal.org/nearblack.html> - Convert nearly 
> black/white borders to exact value."

John,

If gdal_merge.py does what you need then use it.  Gdalwarp is not sensitive
to limited memory the way gdal_merge is, and includes a variety of extra
options like different resampling kernels.  It is really a general purpose
image warper whereas gdal_merge.py is just blatting together whole images into
a mosaic.

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    | President OSGeo, http://osgeo.org