While “one man’s trash is another man’s treasure,” the same types of advanced sensing techniques are used both for investigating archeological sites that frequently reveal much about previous inhabitants from their garbage to true treasure hunts for gold, silver, lost gems and more. Among the more commonly used sensing techniques are magnetometry, electromagnetic induction (EMI or EM), ground penetrating radar (GPR), electrical resistivity tomography (ERT) and light detection and ranging (LiDAR). When combined with real-time position data derived from satellite-based positioning systems, the two- and three-dimensional analysis from sensors provides archeologists and treasure hunters a significant advantage over previous explorers and considerably reduces the time and ambiguity in the search.
Magnetometers are passive sensors that provide non-invasive measurements of the strength and sometimes the direction of a magnetic field. Irregularities in the earth’s magnetic field indicate the location of items made of ferrous material and human activity increases magnetism. For example, old fire pits, bricks, storage pits and even old trenches have higher magnetic readings.
In a detailed magnetic survey, magnetometry provides an effective and efficient geophysical survey technique. It can detect and map archaeological artefacts and features to define areas of past human activity by mapping spatial variations and contrast in the magnetic properties of soil, subsoil and bedrock. It can rather easily be performed over areas of grass, crops and open soil using a multi-sensor cart-based serpentine-path system to survey rather large areas and reveal specific details. While magnetometers do a good job of finding ferrous objects, they do not provide accurate depth information like GPR.
Sensys MXPDA is a 5-channel magnetometer system. Image courtesy of Sensys: http://www.sensysmagnetometer.com/en/mxpda.html
Treasure chest for featured image courtesy of https://www.pinterest.com/pin/430797520580537457/