The HPR 400P system is a stand-alone portable system. It is based around a rugged, splash-proof, shock resistant and “all in one” portable cabinet. The cabinet contains all the surface electronics necessary for underwater positioning. The portable cabinet is equipped with strong carrying handles and has detachable covers at the front and rear. Together with applicable software and a transducer, the system is easy to use by simply interfacing the applicable transducer to the back-plane of the portable unit. A HPR400P system can be directly interfaced to a Differential Global Positioning System (DGPS) receiver, making it possible to give transponder position, Super Short Base Line (SSBL) or vessel positioning, Long Base Line (LBL) in UTM co-ordinates.