The modern multibeam systems, coupled with integrated navigation for ship's guidance, offer the necessary flexibility for both planning and execution of the survey. Kongsberg Simrad's MERLIN and IFREMER's CARAIBES are examples of such systems. The speed of surveying should be kept as close as possible to the range that gives the best and regular coverage athwartship and alongship. This figure is normally 6 to 8 Kn. However this contrasts with ship time availability and normally a compromise is necessary between area coverage and regularity and the fulfillment of the time schedule. The Calibration of a multibeam system is critical and should be performed with great care. The operation is done by collecting data capable to correct any roll, pitch, time biases of the equipment. Suitable areas are flat plains with negligible slope, and steep slopes. On these areas lines are to be repeated and crossed according to the technical specifications and recommendations of the Multibeam System Manufacturer. Moreover, the availability of an accurate position system is required. The knowledge of the Sound velocity in the investigated water column is another critical parameter to be investigated, mainly in areas with consistent seasonal variabilities. This could be done by some strategic measurements of CTD data (or sound velocity), complemented by more frequent XBT profiles, and by a good knowledge of the regional and local oceanography. This latter can be depicted at a rather good scale by using oceanographic data bases like MEDATLAS [11] and WODB [12].
Finally, two dilemmas:
(a) Full Coverage by (gently) following the bathymetric contours or by more rigid straight line patterns?
(b) surveying up slope or along slope?
that can make planning a very complicated task, or have sensible effects on the other geophysical data to be acquired, especially gravimetric or seismic data.