GDAL Raster Merge – How to Merge Thousands of Rasters with gdal_merge.py

gdalmerge

I have several thousands of small rasters, kb size, tens or hundreds of pixels most of them. Batch command of gdal_merge.py can't take all the files at once, so I am doing partial merges of chunks of 500 images, and that's relatively fast.

But when I try to merge the partial merges it takes way too much. In one even gdal_merge.py gave up and returned Killed.

Has anyone experienced something similar, and found an optimization?

Alternatives to gdal_merge.py are welcome

Best Answer

You can create a vrt file with gdalbuildvrt or gdal_merge.py -of VRT and then run gdal_translate -of GTiff on that VRT.

Like this, I had much faster results compared to gdal_merge with huge files.

See this answer to a similar question:

gdal_merge.py loads all files into memory before processing them. therefore it is not able to process large files if your memory is small. see here.

Related Solutions

[GIS] mosaic rasters with gdal_merge.py

The problem is you are passing a list to subprocess then specifying shell=True (which expects a string as input) so it is only taking the first item in the list, which is gdal_merge, and running this. Just running gdal_merge.py gives the same error.

The same code but without shell=True should work:

import subprocess
filea = 'C:/Users/claudio/workspace/test/test1/rasa.tif'
fileb = 'C:/Users/claudio/workspace/test/test1/rasb.tif'
output = 'C:/Users/claudio/workspace/test/test1/output.tif'
subprocess.call(['gdal_merge', '-o' , output, filea, fileb])

[GIS] Merge two rasters with different resolution

Have a look at gdal_merge (http://www.gdal.org/gdal_merge.html). It's a python command so your gdal instance will need have been compiled with python support. It can handle differing resolutions (I believe the output resolution is taken from the first input raster) as long as all input sources are in the same projection. I don't know why gdalwarp is failing on your system but perhaps this is an alternative.

Best Answer

Related Solutions

[GIS] mosaic rasters with gdal_merge.py

[GIS] Merge two rasters with different resolution

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