Optimal Seafloor Mapping Technologies

The primary objective of this proposal is to implement an autonomous swath bathymetry survey capability aboard an unmanned undersea vehicle (UUV) using a hybrid sonar that combines the high spatial resolution of a focused multibeam echo-sounder in a ±30º sector about nadir with the long-range focusing capability of a bathymetric sidescan sonar (Fig. 1) for a total swath angle in excess of 160º (swath width roughly 11 times the UUV’s altitude above the bottom). This represents a better than twofold improvement in swath coverage (hence survey efficiency) over existing solutions that rely on a multibeam sonar system alone, and it fills the near-nadir data gap typical of systems that rely on a bathymetric sidescan sonar alone. In both sonars, dynamic focusing will help constrain the vertical uncertainty associated with each sounding. Likewise, high across-track data density for each ping will provide the redundancy necessary to constrain horizontal uncertainties. For each ping, the achieved swath coverage wlll be defined at the across-track limits where sounding uncertainty exceeds a prescribed threshold. The ping-to-ping evolution of these limits along-track, and the corresponding bottom topography, will be used to estimate the lateral offset of adjacent swaths that minimizes redundancy while maintaining 100% bottom coverage. This method will work best if the UUV maintains a nearly constant altitude above the bottom.