Ground Penetrating Radar (GPR)

Ground penetrating radar (GPR) uses high frequency electromagnetic waves to acquire subsurface information.  Energy is radiated downward into the ground from a transmitter and is reflected back to a receiving antenna. The reflected signals are recorded and produce a continuous cross-sectional “picture” or profile of shallow subsurface conditions. Reflections of the radar wave occur where there is a change in the dielectric constant or electrical conductivity between two materials. Changes in conductivity and in dielectric properties are associated with natural hydrogeologic conditions such as bedding, cementation, moisture, clay content, voids and fractures. Large changes in dielectric properties often exist between geologic materials and man-made structures such as buried utilities or tanks. This method is ideally suited for geotechnical, geophysical and environmental applications, as well as archaeological investigations.  However, it has some limitations like limited penetration depths, and can be used in only specific sediment-bedrock terrains.

Potentials of GPR:

  1. GPR is the only archaeogeophysical method which allows preparation of 2D/3D slices/maps of the underground objects at various depths under the surface without excavation.
  2. It allows precise determination of depths of the underground objects.
  3. It allows the visualization of underground objects as radar images in real time during the measurements.
  4. It allows simultaneous geophysical exploration and archaeological excavation of the registered anomalies.
  5. It has the highest resolution over all other geophysical techniques.
  6. It can be used for scanning of vertical walls and localization of inhomogeneities in it.
  7. Registered signal can undergo for further computing for extraction of invisible details from the raw scan and graphic display of the results.
  8. It allows fast scanning of a large area. It is effective for large scale exploration with high horizontal resolution.
  9. It allows connecting of different archaeological excavations by GPR exploration of the space between them.
  10. GPR exploration can be carried out through different materials (e.g. ice, asphalt, concrete…etc.).
  11. On rough terrains, step-by-step measurements can be carried out which allow deeper penetration of the GPR signals.
  12. It penetrates the subsurface down to ~ 15 - 20 m depth at favorable conditions

    Investigating Near-Surface Cavities using GPR Technology