A Brief Description
Many detection systems use electromagnetic waves to measure a variety of responses. Their frequencies range cover a broad span of the electromagnetic spectrum. Equipment employing electromagnetic (or E.M.) techniques range form satellite imagery to metal detectors and instruments which measure ground conductivity. Very-low to ultra-low frequency instruments are normally used in ground penetrating applications to achieve maximum depth. Time domain EM, sometimes referred to as PULSE E.M. which employs a self contained transmitter-receiver circuit, is used for detection of metallic objects either in water or underground at great depths depending on transmitted power, receiver sensitivity and coil arrangement. E.M. instrumentation is available for satellite deployment, aircraft platforms, shipboard and ground use as well as submarine applications.
E.M. systems are used effectively in mapping geologic formations and a buried mineral deposits. Underwater detection of metallic targets, buried metal objects, archaeological features and subsurface caverns are common applications. E.M. methods are also effective in locating metal accumulations in placer deposits.