Electromagnetic Methods

Electromagnetics uses inductive techniques to measure conductivity of the subsurface without the need of electrodes or ground contact. The methods include frequency domain electromagnetics (Geonics EM-31, EM-34, EM-38 and GSSI Profiler), time domain electromagnetics (Geonics EM-61, Geonics PROTEM systems and White handheld systems), and VLF systems. Depending on the target, the depth of investigation can range from a few meters to several hundred meters.

 EM-31 Survey at the Kennedy Space CenterFrequency Domain systems measure the magnitude and phase of an induced current. The readings can be integrated with a sub-meter GPS system to facilitate quick and accurate data collection. GeoView uses frequency domain electromagnetics to map:

  • Metallic buried debris

  • Conductive (ionic) ground water contamination

  • Archaeological artifacts

  • Mine spoils

  • Variable geological conditions

 

 Time domain systems generate a pulsed current into the ground and measure the decay rate of a secondary magnetic field to determine the bulk conductivity of the subsurface. GeoView uses time domain systems to:

  • Locate unexploded ordinance

  • Locate buried ferrous and non-ferrous metal for environmental and archaeological studies

  • Map saltwater plumes

  • Determine thickness of contaminate plumes

  • Map thickness of geologic strata

  • Locate underground storage tanks

VLF systems measure the local tilt and ellipticity of very low frequency broadcasts. VLF data is used to:

  • Map water bearing fractures

  • Locate ore bodies

  • Locate faults

Click on Samples Below to Enlarge

 

EM-61 Contour Map across a WWII Era Practice Bombing Range

 

 

EM-61 Contour Map Showing UST Locations

 

EM-34 Contour Map Showing Leachate Plume

 

EM-31 Contour Map Showing across a Suspected Landfill