I bet DLPB or someone else could answer this pretty easily...
When a field script sends you to the overworld (world map), it does so by sending you to a Field ID between 1 and 64, which corresponds to field names "wm0" through "wm63". The destination x,y,z in this case is 0,0,0.
Where can I find the world map coordinates that correspond to "wm0" through "wm63"?