True, but that isn't what I was attempting to say.No, that's wrong. Radar will tell you the direction. Always. Even if there's only one station. With multiple stations you can triangulate based on distance alone, but radar sweeps and returns azimuth (direction) information as well. Civilian radar is just broad beam that goes straight out, so when the return radar signal that bounced off the aircraft is absorbed by the dish, the radar records the direction and uses math to calculate how long it's been since it sent out the signal to figure out how far. Military radar uses a narrower beam and uses sweep patterns that allow it to isolate exactly which part of the beam is being returned to calculate what angle the aircraft is at, which can be combined with fancy math to determine altitude and distance in a given direction.
What I heard was that from the automatic updates on aircraft performance (engine temperature, fuel consumption etc. . . ) that are uploaded to a satellite they can tell from how long the handshaking or whatever went on between the satellite and the aircraft, how far from the satellite the aircraft was but not to which side - that gives the two arcs on the map.