Considerations for the Optimal Navigation Pattern from Piling to Piling

The best pattern to move from piling to piling will depend on the presence and orientation of cross bracing and the numbers of rows and columns of pilings, among other considerations.

Each situation should be examined to determine what pattern will work best. In general, the following guidelines can be used:

• The pattern should run perpendicular to the face of the pier.
• The pattern should run parallel to any cross bracing.
• You should avoid navigating the ROV around pilings when moving from one row or column to another.
• You should avoid navigating the ROV through cross bracing whenever possible.
• If you enter a pattern on or near the surface, you should exit on or near the surface to avoid any unseen cross bracing on which the ROV could get hung up.
• The tether handler should deploy the minimum amount of tether to avoid it getting dragged into the piling structure due to wind or currents.
• Be prepared to follow your tether back to the point of obstruction if you get stuck.

An example pattern that follows the guidelines is shown below. The choice whether to do vertical passes, or circumferential passes on each piling can be decided in the field. In this example, it would be best to use vertical passes. Also, in this case because of the cross bracing, it would be best to only inspect one side of each piling, and then do the other side during the next pass of the pattern. Also note that the tether in the pattern below never crosses completely around the backside of a piling,