It seems similar to how GPS is used to find location - you only know the distance from each satellite, not the direction. Contact with one satellite places you

It seems similar to how GPS is used to find location - you only know the distance from each satellite, not the direction. Contact with one satellite places you on an arc (or circle), two sats put you on one of the two spots where the arc around each intersects, and three isolates your position to a single intersection of three arcs at established distances from each satellite. (And four gives you altitude.)