Magnetometers – a valuable tool for underwater surveys – detect the magnetic field anomalies that result when induced magnetic fields are superimposed on the earth’s magnetic field, such as the magnetic anomalies created by ferrous material in the earth’s magnetic field.

Magnetometers are somewhat more difficult to use than SONAR, however they do provide accurate and reliable data. Since magnetometers do not directly measure the physical properties of the areas or objects of interest, the output signals of these sensors require some signal processing for translation into usable data.

Magnetometers are frequently utilized during pipeline surveys, shipwreck surveys, and when buried ferrous materials need to be located. Additional information about objects (such as burial depth) can be gathered by performing statistical analysis on shapes generated from magnetic field anomalies detected by several passes of a single magnetometer or with a multi-magnetometer array. 

See Survey Vessel Orion.