Terrestrial Magnetic Surveys
In terrestrial archaeology, magnetic surveys are typically used for detailed mapping of archaeological features on known archaeological sites. More exceptionally, magnetometers are used for low-resolution exploratory surveys.
Several types of magnetometer are used in terrestrial archaeology. Early surveys, beginning in the 1950s, were conducted with proton precession magnetometers. Data collection with proton precession instruments was slow, making high sample density surveys impracticable. Data were manually recorded and plotted. The subsequent introduction of Fluxgate and cesium vapor magnetomers improved sesitivity, and greatly increased sampling speed, making high resolution surveys of large areas practical. Equally important was the development of computers to handle, process, and display large datasets.
Magnetometers react very strongly to iron and steel, brick, burned soil, and many types of rock, and archaeological features composed of these materials are very detectable. Where these highly magnetic materials do not occur, it is often possible to detect very subtle anomalies caused by disturbed soils or decayed organic materials. Many types of sites and features have been successfully mapped with magnetometers, ranging from very ephemeral prehistoric campsites to large urban centers.
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