Stanford Aeronautical Engineering Professor Steve Rock has served as an Adjunct Scientist at MBARI since the beginnings of the Institute. Over the years, Rock and his graduate students have made many contributions to MBARI’s technology development, particularly including algorithms and software used for the precision controls of robotic systems like ROVs and AUVs. One longstanding project for Rock, his students, and MBARI engineers has been Terrain Relative Navigation (TRN), in which real-time bathymetry measurements are used to navigate an AUV relative to a pre-existing bathymetric map. Navigation of submerged vehicles is difficult because satellite based navigation, like GPS, does not work underwater. Instead, AUVs depend on some combination of inertial navigation and acoustic ranging to beacons at known locations for positioning during missions – in either case achieving precise and accurate navigation is quite expensive. The original motivation for TRN was to enable AUVs with inexpensive navigation systems and simple echosounders to localize relative to a high resolution map, an approach that was demonstrated some years ago. Another use of TRN was as part of a project to simultaneously map and navigate relative to large moving objects, specifically icebergs. This effort led to a NASA funded 2017 expedition using a Dorado AUV with a sideways mounted multibeam to map icebergs in an East Greenland fjord.

More recently, the TRN algorithm is being used with real-time multibeam bathymetry on Mapping AUVs to enable navigating relative to pre-existing surveys with the same 1-meter resolution. At Axial Seamount, we use TRN to exactly repeat prior long baseline surveys so that differencing the old and new data reveals subtle changes in seafloor depth resulting from the inflation of this volcano’s subsurface magma reservoirs. This capability has been transferred to AUV Sentry (operated by the National Deep Submergence Facility of Woods Hole Oceanographic Institution) to enable long term vertical deformation monitoring of this active volcano.