Ifremer's deep-sea ROV Victor 6000 has been equipped with a short range multibeam echosounder in order to accomplish high resolution bathymetric survey for scientific purposes. Specific efforts for the multibeam integration also concern the onboard navigation system as well as the optical high bandwidth data link transmitting data to the surface vessel. The in-line mapping display and data control allowed by the use of an ROV does not reduce the need for data cleaning, correcting and post processing. Ifremer's in-house developed CARAIBES Software© has been used for this step. Three cruises led by international scientific parties have made evident the interest in sub-metric bottom mapping; they are presented in this paper in order to illustrate different kinds of survey strategies. After prototyping and comparison of off-the-shelf multibeam sounders, a permanent survey module is now in project.
Swath bathymetry survey has taken a considerable place in the scientific programme of Victor 6000. The implementation of multibeam sonar (MBS) on the ROV will be described as a system approach with several technical details : the high bandwidth data link between the acoustic head and the sonar processor - transmitting data through 8km of cable; underwater navigation and acoustic positioning; depth, attitude and heading measurement. Three different models of multibeam sonar have been employed at depths between 600 and 1700m, some of them on the same survey site for comparison : RESON's Seabat 8101 and 8125, and SIMRAD's EM-2000. On one hand, the ROV is strongly limited in speed, not allowing to travel significantly more than 1 km/h (mean survey track during a dive), it constrains the surface vessel and requires operators and ROV pilots. On the other hand, gathered data are visible in real-time and rough quality control on the fly is possible.
