I'm probably missing something, but aren't you basically looking for node positions? Node positions are local to the vehicle reference system, so you can do vehicle_pos + node_pos to get what you want (from what I understand at least)
I tried doing that at one point, but the resulting position seemed to drift around within a foot or so of the actual node depending on the vehicle's movement and orientation. Perhaps I made a silly error on my end. I can try to record this happening.
