Definition

A type of SWATH(E) SOUNDING SYSTEM in which the equipment emits a timed PULSE of sound that is narrow in the fore-aft direction and wide in the across-track direction. The system samples the reflected sound hundreds or even thousands of times for each emission. For each sample, the PHASE difference of the reflected sound arriving at two (or more) RECEIVERs located a known distance apart is measured and used to compute the ACOUSTIC angle of arrival.  Also, the time difference between the emission and reception for each sample is converted to a RANGE.  Geometry is then used to convert each RANGE and angle to DEPTHs and also to position these DEPTHs within the SWATH(E) on the SEAFLOOR.