How to Find Buried Objects
[The text in this article has been extracted from a publication by the United States Environmental Protection Agency.]
Magnetometers are useful for locating buried objects made of ferrous materials. Although highly sensitive magnetometers have been developed that can detect the void space within large buried objects of any material (e.g., fiberglass tanks), this technology is not often used because many cultural interferences will mask the effect.
Magnetometers measure the earth's total magnetic field at a particular location. Buried ferrous materials distort the magnetic field, creating a magnetic anomaly.
Magnetometers are very fast and relatively inexpensive.
Potential cultural interferences include steel fences, vehicles, buildings, iron debris, natural soil minerals, and underground utilities.
Power lines are an additional source of interference that can be neutralized with the use of very sophisticated equipment that synchronizes readings with the oscillating electrical current.
Some magnetometers are very simple and do not have a data recording or processing ability. They indicate the presence of iron with a sound or meter and can be used as a rapid screening tool.
Magnetometers that record data can, with the aid of data processing software, be used to estimate the size and depth of ferrous targets.