[gdal-dev] Merge and Overviews with VSIMEM

[Even Rouault]

> When I attempt to call it, using the following, the `vsimem` object seems
> to no longer be accessible to perform the overview creation:

Yes, /vsimem/ objects are only visible during the lifetime of the process. 
Here as you start a subprocss, the /vsimem file will not be visible by the 
parent

Different possible solutions:
- you materialize the file on the filesystem
- or you import gdal_merge, and run gdal_merge.main(argv)
- or you use gdal.Warp() instead of gdal_merge

-- 
Spatialys - Geospatial professional services
http://www.spatialys.com