Sorry but gmap3d.img is usually locked and version dependant, probably you mean gmapdem.img that is unlocked and not version dependant.
gmap3d.img shows cities buildings pictures on map when you zoom in, DEM map shows 3d terrain shadings.
NT and NTU have different FID and different gmap3d with different FID. All addition files are version dependant because they contain their version FID.
This is the reason you must use CNEU NTU if you want JCV.
NT version doesnt provide a working JCV for SP.

Separate jcv files exist and G Express downloads them when users have lifetime for one region only. You cant build them by yourself, but in CNEU threads usually some users post them along separate regions imgs.

sent with my phone