A new pitch/yaw stabilized bathymetric survey system

There is an increasing need in the oil and gas industry, as well as the ocean research community, for mid to deep ocean survey systems that compensate fully for vessel pitch, roll and yaw motion. To respond to this requirement, L-3 Communications SeaBeam Instruments/ELAC Nautik are developing a new wide swath bathymetric sonar system. This system will use a two-dimensional projector array to concentrate the transmit beam in the athwart ship direction as well as the along track direction. By continuously sweeping this concentrated beam in the athwart ship direction while adjusting for ship´s motion, complete compensation for pitch and yaw is achieved. As the ship advances, the seafloor is scanned in a series of parallel lines, analogous to a progressive scan CRT. The swept beam technique uses a single sonar frequency to ensonify the entire swath. It is therefore compatible with existing receiver hardware and echo signal processing software. This reduces the development required to implement the new transmitter in a bathymetric system. It also offers advantages in the shallow regions of operation relative to multiple frequency “sector scanned” operation, in that it can be applied at the shortest pulse widths consistent with frequency and array size. This allows not only full pitch and yaw compensation over the entire range of operation, but also opens the possibility for near field focusing, allowing the system to maintain its maximum resolution to its shallowest operating depth. The beam sweeps from one side of the swath to the other through a series of intermediate waypoints. The waypoints are at fixed across track angles. The angles with respect to the projector array are calculated dynamically each ping to compensate for vessel motion