Ground Penetrating Radar (GPR)

Ground Penetrating Radar

Ground-penetrating radar (GPR) is a geophysical method that uses radar pulses to image the subsurface. This non-destructive method uses electromagnetic radiation in the microwave band (UHF/VHF frequencies) of the radio spectrum, and detects the reflected signals from subsurface structures. GPR can be used in a variety of media, including rock, soil, ice, fresh water, pavements and structures. It can detect objects, changes in material, and voids and cracks.

GPR uses high-frequency (usually polarized) radio waves and transmits into the ground. When the wave hits a buried object or a boundary with different dielectric constants, the receiving antenna records variations in the reflected return signal.

The depth range of GPR is limited by the electrical conductivity of the ground, the transmitted center frequency and the radiated power. As conductivity increases, the penetration depth decreases. This is because the electromagnetic energy is more quickly dissipated into heat, causing a loss in signal strength at depth. Higher frequencies do not penetrate as far as lower frequencies, but give better resolution. Optimal depth penetration is achieved in ice where the depth of penetration can achieve several hundred meters. Good penetration is also achieved in dry sandy soils or massive dry materials such as granite, limestone, and concrete where the depth of penetration could be up to 15 m. In moist and/or clay-laden soils and soils with high electrical conductivity, penetration is sometimes only a few centimetres.

APPLICATIONS
  1. Earth sciences - to study bedrock, soils, groundwater, and ice.
  2. Engineering - non-destructive testing of structures and pavements, locating buried structures and utility lines, and studying soils and bedrock.
  3. Environmental - to define landfills, contaminant plumes, and other remediation sites.
  4. Archaeology - for mapping archaeological features and cemeteries.
  5. Law enforcement - for locating clandestine graves and buried evidence.
  6. Military - for detection of mines, unexploded ordnance, and tunnels.
ADVANTAGES
  1. Fast data collection/surveying speed.
  2. Able to detect voids and trenches.
  3. Able to determine depths (vertical) and lengths (lateral) of targets.
  4. Multiple application uses.
  5. Non-destructive.
DISADVANTAGES
  1. Terrain must be flat and even
  2. Limited by conductive ground such as clay or areas of salt-water intrusion.
  3. Generally, shallow depth of observation.
  4. Site specific applications.
EQUIPMENT

Sensors & Software's NOGGIN subsurface imaging instruments and pulseEKKO systems offer a wide range of frequencies to accommodate numerous applications.