[gdal-dev] Re: gdalwarp fills nulls?

[Hermann Peifer]

> Selon Greg Coats <gregcoats at mac.com>:
> 
> -wm is an option specific to gdalwarp. Here's detailed explanation :
> http://trac.osgeo.org/gdal/wiki/UserDocs/GdalWarp#WarpandCacheMemory:TechnicalDetails
> 

Just to add that the default value is 64MB of RAM, see the snippet below, which I took from 
http://trac.osgeo.org/gdal/browser/trunk/gdal/alg/gdalwarpoperation.cpp

498 	/* -------------------------------------------------------------------- */
499 	/*      Default memory available.                                       */
500 	/*                                                                      */
501 	/*      For now we default to 64MB of RAM, but eventually we should     */
502 	/*      try various schemes to query physical RAM.  This can            */
503 	/*      certainly be done on Win32 and Linux.                           */
504 	/* -------------------------------------------------------------------- */
505 	    if( psOptions->dfWarpMemoryLimit == 0.0 )
506 	    {
507 	        psOptions->dfWarpMemoryLimit = 64.0 * 1024*1024;
508 	    }


One thing I learnt recently is that increasing the -wm value is counter-productive when warping small tiles into a big mosaic.

Hermann