If you have light barriers across the space the person is supposed to travel (one every 2-3 feet, or one every 0.5/1m), then at some point one of the barriers is blocked. If the next barrier to be blocked is in one direction, it means the person is travelling in that direction. If no barrier is obstructed, the person is standing between two barriers (if they are so far apart, that a person can fit between them), but he/she is closest to the barrier that was last obstructed.