The idea was to merge into 1 geotiff 28 irregular shaped geotiffs which ranged in size from 1g up to 13g and making up a total of 113g. Why? Because I then needed to cut the resulting geotiff into multiple irregular shaped individual geotiff’s. This took a couple of days, and I was quite keen to come home today as this morning it was at 80%, you can only imagine my disappointment when I checked and found…

0...10...20...30...40...50...60...70...80...90..Traceback (most recent call last):
  File "/usr/bin/gdal_merge.py", line 540, in <module>
    sys.exit(main())
  File "/usr/bin/gdal_merge.py", line 526, in main
    fi.copy_into( t_fh, band, band, nodata )
  File "/usr/bin/gdal_merge.py", line 270, in copy_into
    nodata_arg )
File "/usr/bin/gdal_merge.py", line 63, in raster_copy
    nodata )
  File "/usr/bin/gdal_merge.py", line 105, in raster_copy_with_nodata
    nodata_test = Numeric.equal(data_src,nodata)
MemoryError

This as you can imagine was very frustrating, and I just assumed that the output was junk but figured what the hell, its created a 301G file lets see what it is. Started the process to load into Qgis, and since I figured it would take a while started this blog post. It seems though that output might be useful as qgis eventually loaded the file, and it actually looks like what I expected. So first things first I have set qgis to now save the file under a new name… Its going to take a while, currently at 12.2G and I actually expect it to end up bigger than the initial 301G

… a day or so later …

So it turns out the merge worked, I will revisit why the error later, but the file saved by qgis had the exact same size, and has the same result using gdalinfo. AND i have just done my first clip BUT  it seems I made a mistake the command I used was

gdalwarp -dstnodata 0 \
-q -cutline shape_file_to_clip_to.shp -tr 0.05806 0.05806 \
-of GTiff input_file.tif \
clipped_file.tif

Which resulted in a file the same size of the input file, and the same dimentions, what I should have done, I think, is:

gdalwarp -dstnodata 0 \
-q -cutline shape_file_to_clip_to.shp -tr 0.05806 0.05806 \
-of GTiff input_file.tif \
clipped_file.tif

Which is what I am running now, the previous command took about 3 hours!