Ship hulls are inspected to determine if explosives or contraband (usually narcotics) are attached. Parasitic containers for smuggling narcotics may be secured to bow thrusters, bilge keels or rudder
structures. Magnetic mines may be attached anywhere to a steel hull below the waterline. Inspections are typically conducted using clearance divers or ROVs equipped with underwater cameras and sonar.
There are a number of challenges to conducting hull inspections underwater. Searches are carried out under conditions of limited or near zero visibility, severely limiting the range of underwater cameras.
Hull shapes can be complex making orientation and navigation difficult for both divers and underwater vehicles. Metal hulls produce strong sonar returns and multipath effects adding to the challenges
of inspecting these vessels using sonar. When using pole mount cameras or sonar for hull searches coverage will be limited depending on the depth of the hull being examined and the length of the pole
A remotely operated underwater vehicle (ROV) is the preferred platform for hull inspections using underwater cameras and sonar. Vessel inspections can be completed in far less time than diver searches
with little or no risk using M3 Multimode Multibeam Sonar mounted on an ROV platform. Sonar is positioned most easily by using an ROV with sufficient power to hold against currents and to press the structure
of the ROV against the hull. This provides a steady platform for the sonar and enables high quality scans that readily define smaller foreign objects attached to hull structures. Merging the scans together
using a commercial software package can provide a complete picture of the ship’s hull, verifying the areas scanned are clear, and documenting that areas have not been missed.
The Kongsberg M3 sonar is an ideal solution for vessel hull inspection, capable of rendering complete vessel hull imagery that can detect foreign objects with sub-meter detection using the EIQ (enhanced
image quality) mode. The M3 sonar itself is lightweight, hand portable, and easily mounted on an ROV, with Ethernet communications using the vehicle’s umbilical. Operation is through a COTS laptop or
desk top computer. The M3 sonar can easily be used by a single ROV operator to perform a complete bow – to stern vessel hull inspection and present data as a single (mosaicked) image that provides a complete
view of the submerged portion of any vessel.