Magnetometers for Underwater Surveys
Another valuable tool for underwater surveys is the magnetometer. When a ferrous material is placed within an existing magnetic field (such as the earth’s magnetic field), it develops an induced magnetic field. An induced magnetic field that is superimposed on the earth’s magnetic field creates a magnetic field anomaly. Magnetometers are employed to detect such anomalies.
Since magnetometers differ from many other instruments in that they do not directly measure the physical property of the area or objects of interest, the output signal of these sensors requires some signal processing for translation into usable data.
Magnetometers are somewhat more difficult to use than SONAR, however they do provide accurate and reliable data. Magnetometers are frequently utilized during pipeline surveys, shipwreck surveys and whenever buried ferrous materials need to be located. Additional information about objects (such as burial depth) may 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.
