Synthetic long baseline navigation of underwater vehicles

This paper describes a new concept (patent pending) for accurate autonomous deep-water navigation of underwater vehicles (UV's) for extended periods of time. The concept is called Synthetic Long Baseline (SLBL) and is based on the combination of dead-reckoning (DR) and acoustic range and/or range rate measurements from a single acoustic source, e.g. a transponder moored to the sea floor. Focus is kept on a simple form of SLBL (see Figure 1), which can be implemented using existing commercial-off-the-shelf (COTS) components. Combined with a high performance dead-reckoning navigation system, SLBL provides adequate accuracy and redundancy to eliminate the need for a USBL equipped survey ship or a full LBL transponder network, even on long duration deep water surveys. Some level of redundancy is incorporated, which permits quality control of navigation data. Experimental results, from accuracy verification tests of he high performance doppler-inertial dead-reckoning based navigation system MARPOS(R) [15], suggests that SLBL will provide sub-meter positioning accuracy for 1 x 1 km site surveys using a single transponder as the reference point. The performance is almost independent of water depth. The presented SLBL system may also allow for highly accurate and cost-efficient pipeline surveys and a variety of other applications. Sea trials of the first system are scheduled for August 2000 onboard the MARIDAN-600 series of AUV's.