If it accurately records GPS data, best case scenario would be to tape your phone on the bottom of your drivers side door (in America) and get the closest to the center line elevation as possible. But think about it, Kaz will HAVE to give us track editing of the GPS data otherwise its IMPOSSIBLE to add banking from your cell phone GPS scans. How lame would that be that it produces hilly roads that remain at ZERO degrees from the left side of the road to the right.
If we record the gps data, you should also bring a video recorder and mount to dash. Ideally the game auto generates the elevations and turns of the track, then you use your video footage to apply road width and banking at various points along the track. Guys with attention to detail like myself, thats all Id need and PRESTO Pacific Coast Highway in GT6!