SHARPS II: Precision Navigation Sonar for Undersea Vehicles
Since the late 1980s I've been working on the technology of high precision ranging and navigation underwater. The latest version of includes spread-spectrum signal processing and a DSP to achieve 
sub-centimeter measurement accuracies, a kind of super-fine underwater GPS, which allows an undersea vehicle to hover and run very precise tracklines and generate precise maps of theocean floor. The technology is now marketed by Marine Sonic Technology of Gloucester Virginia and has been purchased by the Woods Hole Oceanographic Institution, MIT, and a variety of other institutions.
The system has recently been integrated into Woods Hole's JASON remotely operated vehicle system to keep track of two vehicles underwater:
B. Bingham, D. Mindell, T. Wilcox, and Andy Bowen, "Integrating SHARPS II precision navigation Into JASON/MEDEA two-vehicle operation", Proceedings of the MTS/IEEE OCEANS 2005.
B. Bingham, D. Mindell, T. Wilcox, and A. Bowen, "Integrating precision relative positioning into JASON/MEDEA ROV operations", Marine Technology Society (MTS) Journal, vol. 40, no. 1, pp. 87-96, Spring 2006
B. Bingham, D.A. Mindell, D.Yoerger, B.P. Foley and W.Seering, "Acoustic multipath identification with expectation-maximization," IEEE/MTS Oceans Conference, Sept. 2003.