Can anyone confirm the best map datum to use in central Vietnam.

I believe it would be either SASIN or IND54

How come GPS' can't find the right satellites themselves?
What happens when travelling long distances where the map datum changes?

My recommendation is Keep it Simple...use WGS84 everywhere...there is little need for country/region specific datums unless you are trying a match a datum used on a particular map.

Thanks, makes sense now