Color-shaded relief GeoTIFF image of interferometric sonar data collected by the USGS within Red Brook Harbor, MA, 2009 (RB_BathyShadedRelief_5m, 5-meter cell size)

Bathymetric and backscatter data were collected using a Systems Engineering and Assessment, Ltd. SWATHplus (234 kHz) interferometric sonar system. The SWATHplus transducers were mounted on a rigid pole, approximately 0.5 m below the water line, from the bow of the of the R/V Rafael of Woods Hole, MA. A CodaOctopus F-180 Attitude and Positioning System, mounted directly above the SWATHplus transducers, measured vertical displacement (heave) and attitude (pitch and roll) of the vessel during data acquisition. An Applied Microsystems Ltd. Micro SV sound velocimeter, mounted adjacent to the SWATHplus transducers, continually measured changes in sound-velocity near the sea surface, and a hand-casted, Applied MicroSystems SV Plus sound velocimeter was used to collect sound-velocity profiles of the entire water column at least once each survey day. SWATHplus acquisition software was used to control the transducers and digitally log sonar data across an 80 m swath in SWATHplus raw (SXR) format. An RTK-corrected GPS signal was transmitted to a beacon aboard the survey vessel once every second from a base station established by USGS personnel in the inner harbor. RTK vertical heights were used to correct tidal offsets during post-processing. To obtain 100 percent coverage of the seafloor, survey lines were spaced approximately 30 m apart. The R/V Rafael maintained an average speed of 5 knots during survey operations.