In-situ Underway Sound Velocity Profiling for Calibration of Multibeam Sounders Using a Moving Vessel Profiler (MVP)

The Canadian Hydrographic Service (CHS). as with many other organisations involved in ocean based research, is faced with the requirement to collect water co lumn data profiles for a variety of reasons. The CHS's specific need is the co l-lection of sound velocity profiles for the day-to-day measurement of the changing water column wh ile operating multi-beam sounders. Increasing pressures to improve the economic efficiency of survey operations and the quality of the data collected have led to the development of a family of tools to collect near vertical water column profiles from a moving vessel. These systems consist of a comput-er controlled hydraulic (or electric) winch, overboarding system and free fall fish capable of carrying a variety of instrumentat ion. The MVP is capable of collecting profiles at ship speeds up to 12 knots and includes two modes of operation, a repetitive mode with adjustable time delay between casts or manually initiated mode. The control system includes bottom avoidance and real time feedback of free fall f ish depth. Although the CHS 's primary need was for Sound Velocity (SV) profiling, other pay