Importing large GADM vector data

Q: How do I import very large data into GRASS GIS? I.e. from GADM

A: In contrast to the older GADM v1, GADM v2 contains a lot of floating point representation errors in the coordinates, most probably caused by the software used to create GADM v2. You need to perform additional cleaning with snapping to a very small threshold, i.e.

v.in.ogr ... snap=1e-7

Important: You should use the improved GRASS GIS 7 for the import of large vector data, because the import may not work with GRASS GIS 6.