A magnetometer is used to measure the intensity of the earth's magnetic field.  Deviations of magnetic intensity are caused by changes in concentrations of natural ferrous minerals (e.g. magnetite) or by the presence of ferrous metals.

Magnetic measurements can be used for geologic mapping to provide an estimate of the thickness of non-magnetic sediments overlying magnetic rock and location of structure and faults within magnetic rock.  Magnetic measurements are commonly used for locating and mapping buried ferrous metals (i.e. metal wastes, drums or underground tanks and utilities).  Magnetics is also used for detection of unexploded ordnance (UXO).

Applications

• Identify natural and man-made ferrous objects
• Map geologic structure and stratigraphy
• Map karst features within magnetic soils and rock

Advantages

• Measurements are relatively easy to make
• Does not require intrusive ground contact
• Carried by hand or vehicle-mounted

Limitations

• Susceptible to interference from steel pipes, fences, vehicles and buildings
• Total field measurements susceptible to natural fluctuations in Earth's magnetic field (a base station must be used to remove natural fluctuations in Earth's field)