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10 st / August 2015 www.sea-technology.com and maneuverability of the vessel enables safe operations around shorelines and hazards. This type of survey vessel requires a compact so- nar head that can be pole mounted and interfaced with a variety of ancillary position, heading and motion sensors. The single-beam echo- sounder was the survey tool of choice once acoustic technology was accepted into the feld, and is still in use today. Following that, and more common today, the multibeam echosounder (MBES, or beamformer), originally developed A detailed knowledge of shallow-water bathymetry is vital for a wide range of marine activities. Surveys are required for navigation channels, dredge works, lake and dam management, environmen- tal mapping, marine archaeol- ogy, pipeline and cable routes, and offshore construction. These surveys are typically carried out by small vessels of opportunity, often oper- ating in less than 20 m of water. The current technology utilized for this type of work is typically ineffcient and costly due to the design of these legacy instruments. This ineffciency has manufacturers ex- ploring new innovations in swath bathymetry systems and has led EdgeTech to the development of a novel swath so- nar technology, the multiphase echosounder (MPES). This article describes the technology behind the MPES, with ex- amples from a recent survey trial to demonstrate the advan- tages over traditional systems and show the new technique's bathymetric accuracy. Background A wide-swath sonar mounted on a small survey vessel is an accepted solution for high-resolution full coverage sur- veys in the nearshore environment, where the shallow draft Multiphase Echosounder to Improve Shallow-Water Surveys Hybrid Approach to Produce Bathymetry and Side Scan Data By Lisa Brisson • Dr. Tom Hiller (Top) Co-registered bathymetry and high-resolution side scan imagery of mooring blocks along the seafoor in a sheltered marina. The data were captured by a 550-kHz system. (Bot- tom) Co-registered bathymetry and high-resolution side scan imagery of eel grass. Water depth is less than 1 meter at chart datum. The data were captured by an EdgeTech 6205 550-kHz/1,600-kHz model.