Sonar map
From Tomb Raider Wiki
Lara uses a sonar map in Tomb Raider Underworld to find her way around in the exotic locales she visits.
The sonar map shows a sort of non-textured 3D view of the game, showing an average of where you are. It isn't very useful and only gives you a basic idea of where to go,sometimes even more complicated than not using it.
It is kind of useless in the game itself, not really helping in the way it was said it would do.
