In general, the hydrophone are used to calculate the delay between the reception of a ping from the reference to the 3 other hydrophones. With the phase difference, we can get the angle (heading) for the X reference on the submarine and the angle bewteen the X and Y plan and the pinger. These 2 angles are used to navigate at 2 positions. Only the heading would be necessary for the competition, but the system is more reliable with the 2 angles and it is easier to confirm the mouvement of the submarine.