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. To be able to use imported data in GRASS GIS 6, just rebuild vector topology (e.g., ).