Towfish altitude computation using multipath acoustic ranging

A technique that uses an acoustic ranging method to estimate towfish altitude, i.e., the height of the towfish above the seafloor, is presented. The ranging algorithm is an implementation of path-length calculation for acoustic signals generated at the towfish and received by a hydrophone located at the towing ship. The time delay between the direct and bottom-reflected signals is measured. By knowing the towfish depth and layback distance, the time delay can be used to compute the towfish altitude