Felix Schalck wrote:
Hello,
As explained in my previous question, I'm trying to create a high
resolution topographic map of europe based on cgiar processed srtm
data. Of cours, the first step is to merge the 5*5° tif tiles into one
big tif, which can be achieved using gdalwarp's mosaic feature.
Simply pasting all the tiles togther trough following code:
gdalwarp --config GDAL_CACHEMAX 512 -wm 512 HDA1/srtm_*.ti HDA2/final.tif
takes about 20 hours. HDA1/2 are two different harddrives.
Now, a second script, pasting first "slices" of 5*30° together, and
than merging all the slices:
for i in 39 40 41 42 43; do
gdalwarp --config GDAL_CACHEMAX 512 -wm 512 HDA1/srtm_$i*.tif
HDA2/slice_0$((i-34)).tif
done
gdalwarp --config GDAL_CACHEMAX 512 -wm 512 HDA2/slice_*.tif HDA1/final.tif
takes less than on hour ! Filesize is similar.
So what is the trick here ? Is there some quality loss when using gdalwarp ?
Felix Schalck
I have the same observation while working with ASTER GDEM tiles (1x1 degree
tiles, 3601x3601 pixel each). When warping/merging, say: 10 tiles into a single
outfile.tif, then it takes gdalwarp around 5 seconds per tile to do the job:
gdalwarp --config GDAL_CACHEMAX 500 -wm 500 \
-rb -srcnodata -9999 -dstnodata -9999 \
-t_srs etrs89_laea_52_10.wkt \
-tr 100 100 \
ASTGTM_N51*.tif outfile.tif
When trying to do the same with some 200-300 input files, then it takes several
minutes to process 1 tile. My area of interest translates roughly into 1500
ASTER GDEM tiles... :-(
Hermann
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