Multibeam echo sounder, sidescan sonar, multiprobe gradiometer and subbottom profiler
By being dragged along by a survey vessel, these geophysical measuring techniques make it possible to create detailed maps of the waterbottom.
The multibeam echo sounder maps the water depth; local deviations in detph may indicate the presence of a large object on the waterbottom,
The sidescan sonar is even more accurate in visualizing objects on the bottom of the sea in great detail.
The multiprobe gradiometer determines whether the objects detected by the multibeam echo sounder and sidescan sonar consist of ferrous material. It's magnetometers are also able to look several meters deep into the water bottom.
The Sub-Bottom Profiler is an acoustic technique that maps the water bottom by dragging the probe over the surface or over the water bed. With this technique, depending on the desired accuracy, water bottoms can be mapped up to tens of meters, detecting obstacles on or under the water bottom.
ROV and AUV
Offshore UXO surveys are performed from a ship using an ROV (remotely operated underwater vehicle) and/or an AUV (autonomous underwater vehicle) equippede with several measuring techniques. The ROV for example is equipped with a rack of 8 to 12 gradiometer probes, a short-range sonar and a camera.