Marine magnetometers detect variations in the Earth's total magnetic field. These variations may be caused by the presence of ferrous material on or under the seabed, geological features or diurnal variations in the Earth's magnetic field due to solar activity. Marine magnetic surveying has become a standard technique for mapping the location of ferrous material on the seabed.
Magnetometers are usually towed behind the survey vessel at a sufficient distance to avoid any magnetic disturbance caused by the survey vessel itself.
For the 2003 fieldwork, a Geometrics G-881 caesium vapour magnetometer was deployed on each wrecksite at a linespacing in the order of 10-20m.
In the course of post processing the magnetometer data was imported into Fledermaus and overlayed over multibeam data to show the relationship between the anomaly and the visible wreck site.