(so skip those naval maps)
One's dreamself is not to be confused with the astral body, nor is the place a perfect replica of the place transported to; both things (called dreamentities) are generalizations made by all the people (and beings) dreaming about that place (and you) at the same time.
So, in order to visit that place depicted on that map you went to bed with, there must...
- ...be people dreaming about you (to form your dreamself)
- ...be people dreaming about the place on your map (to form the dreamentity of that place)
Generalizations are almost never true. Your dreamself may very well end up being big-headed (literally) if that's how the people dreaming about you feels about you.
The same goes for the place. If nobody's dreaming about your destination - but enough people are dreaming about you - your dreamself will end up in the Hall of the Mare, a black void consisting only of a dimly lit throne, upon which the Queen Mare sits and stares at you with her terrible multitude of eyes until you awake. Each failed teleportation will anger her; fail enough times and she will rise from her throne on her spiderlike legs, perforating the membrane that separates the Mare and our world. She leaves you there, alone in the hall, but you know she's probably out to do something to your physical body.
Where do you want to go tonight?