Multibeam Roll vs Swath Width - how roll kills hydrographic survey productivity

Roll Stabilization Makes You Money … if you are a hydrographic surveyor

Bottom Line Up Front:  A vessel that rolls less covers more ground…273% more in this case.

Modern multibeam echo sounders are incredible in that they can use beam steering to counteract roll motions in order to maintain the swath of a survey line.  But….there’s always a catch.  Beam steering can only occur within the bounds of the multibeam echo sounder’s maximum swath angle (160° in this case).  If you have a stable vessel that exhibits roll within -3° to 3°, you can theoretically still utilize 154° of your maximum swath angle.  In contrast, if your vessel experiences -30° to 30° of roll, even if only occasionally, only 100° of swath angle could be used.

This graph illustrates how a survey vessel’s roll impacts the maximum swath width of a multibeam echo sounder.  While required sounding density and other factors may also influence swath widths, they can never be wider than the motion of the vessel permits.

The graph compares the effect of roll amplitudes on maximum multibeam swath widths in 50m water depth.  The callouts are to illustrate the relative performance of different hull types in a 2m sea state.  There is a 273% increase in swath width when comparing a 150° swath angle with a 100° swath angle.  Simply put; a 14 day job for a less stable vessel could be a 5 day job for a more stable vessel.  When you think about the implications roll on Health Safety & Environment (HSE) and ultimately on profitability, it is imprudent to ignore.

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