What is Remote Sensing?
Remote sensing is a method for detecting objects in soil, water, or other mediums without being physically present next to them. Each remote sensing technique uses different waves to detect objects at a distance.
This device is used to find wooden shipwrecks by detecting iron objects used in the ship's construction such as nails, ironwork or artillery. It was developed during the Second World War as a means of locating German submarines.
The magnetometer has a variety of uses in underwater archaeology - in large scale survey it is towed behind a boat to locate a submerged site. In more intensive surveys of a wreck site the magnetometer is used to chart remains, point by point, even if these are buried below sediment (magnetometer equipment can penetrate sediment build-up over objects).
When wrecks are not completely buried under sediment they can be found using a technique referred to as side-scan sonar. Side-scan sonar is similar to radar but used in an underwater environment. Objects such as ships or other large artifacts projecting from the ocean floor or lake bed will appear as shadows visible on the instrument screen. In the case of the Hamilton and the Scourge side-scan sonar showed that these ships rested intact with masts erect under almost 300 feet of water.
New Search and Survey Technology
The use of fibre optic and digital signals has ushered in a new phase of underwater surveying techniques. Now side-scan sonar can be used with effectiveness to any oceanic depth. Other techniques such as sub-bottom profilers enable the viewer to 'see' below the ocean floor or lake bed and detect non-metallic objects or ships that are fully buried.
Notes from Underwater Archaeology - Exploring the World Beneath the Sea by John-Yves Blot, 1996, Thames and Hudson