[Gdal-dev] gdalwarp -rn(default) vs -rc

[John Mitchell]

Hi,
Within gdalwarp where does using the higher quality option of -rc(cubic
resampling) verses the default of nearest neighbour resampling have the
greatest impact as far as quality and also as far as speed.
Either
a.) running gdalwarp to mosaic a number of tiles together and at the same
time reproject
  i.e.  gdalwarp.exe -wo SKIP_NOSOURCE=YES  -s_srs EPSG:" + EPSG + " -t_srs
EPSG:" + EPSG_wgs84 + " -rc -co tiled=yes -q " + inputFiles + " " +
rasterFile
b.) running gdalwarp to reduce the resolution but not changing the
projection and not mosaicking
 i.e.  gdalwarp.exe -tr " + psx + " " + psy + "  -s_srs EPSG:" + EPSG_wgs84
+ " -t_srs EPSG:" + EPSG_wgs84 + " -rc -co tiled=yes -q " + rasterFile + " "
+ warpedSplitRasterFile
Will it be faster to reduce resolution against a file via gdalwarp that has
already been reduced and will the quality be the same?  As an example:
1.) I mosaic a number of tiles at full resolution
2.) I reduce the mosaic from 1 by 1/2
3a.) I reduce the mosaic from 1 by 1/4
3b.) I reduce the mosaic from 2 by 1/2

Between 3a and 3b will 3b be faster and will the quality be the same?

Any other suggestions on speeding up gdalwarp would be appreciated.

Thanks,

-- 
John J. Mitchell
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