The science of hydrography has changed much over the last century and even the last few decades. New technologies in sonar, horizontal control and GPS, and computers continue to have the potential to change standard survey practices and increase efficiencies. Phase Differencing Bathymetric Sonar NOAA’s Office of Coast Survey (OCS) is currently engaged in the evaluation of phase differencing bathymetric sonar (PDBS) technology for possible use in nautical charting hydrographic survey work.Studies of several commercially available PDBS systems indicate that they provide high quality data while significantly increasing efficiency and safety of operations in nearshore and very shallow water areas. These gains in efficiency and safety are attributable to the wider swath width that interferometric sonars produce relative to shallow water multibeam systems in areas shoaler than ~20m. This increased swath width appears to enable hydrographers to survey more than twice the shallow water area per given time and allow vessel operators to stand further off of hazardous features and the shoreline while acquiring a denser dataset than is feasible with technologies in use today. OCS recently procured a PDBS system for operational test and evaluation and integration into the existing nautical charting data acquisition and processing pipeline. RESOURCES Coast Survey Development Lab Phase Differencing Bathymetric Sonar page Center for Coastal and Ocean Mapping:  Joint Hydrographic Center