Frequency Domain EM (FDEM) is a technique in which electric and magnetic (EM) fields are induced into the ground by applying AC signals at multiple frequencies via a transmitter coil and then analyzing the resulting electrical or magnetic response by a receiver coil. By observing the response as a function of frequency, you not only get a spectrum of how the material behaves dynamically, but also at depth. This data is usually represented by two components. The Quadrature which provides a direct reading of apparent soil conductivity and In-phase which measures magnetic susceptibility. System options include multi-frequency sensors for shallow lateral mapping and horizontal loop sensors for Slingram type profiling modes. FDEM offers an efficient way to map laterally with high spatial resolution across wide area sites. Common applications include environmental contaminant plume mapping, salinity, groundwater, agricultural, geotechnical and archaeological.