Abstract: A navigation system extends satellite navigation to divers, underwater vehicles, and surface vessels. The navigation system comprises a location reference unit and a plurality of sub-surface beacon units. The location reference unit includes a receiver to receive navigation signals from earth-orbiting satellites and/or an inertial navigation system. The location reference unit further includes control circuits to communicate with to sub-surface beacon units and to transmit location information to said sub-surface beacon units, and a transceiver to transmit location information to the sub-surface beacon units. The beacon units include control circuits to determine the location of the beacon unit based on location information received from the location reference unit, and a transceiver to receive location information from the location reference unit and to transmit location information to a guided unit to provide navigation assistance to the guided unit.

Abstract: A diver unit computes the direction and distance to a specified target. When the target is obstructed, the diver unit receives navigation assistance data from another diver unit. The navigation assistance data includes direction information that is referenced to a common reference line extending between the two diver units.