Surveying near-surface structures using ground radar
Radiograph of a profile with slight topography over a groundwater horizon with the 40 MHz antenna.
Source: BGR
Georadar is widely used for the exploration of near-surface structures. It can find cables, cavities, belts of soil water and geological layers. Depending on the application, the measuring frequencies used are between a few megahertz and some gigahertz. Depending on the measuring frequency, the resolution of the measurements is some meters to some centimetres. The possible measuring penetration depth depends on the frequency and also strongly on the conductivity and dielectricity of the medium. In Antarctic ice, which has a very low conductivity, a penetration depth of several kilometres is possible, whereas highly conductive soils saturated with saltwater only allow a penetration depth of some centimetres. BGR uses several measuring systems. A pulse radar system that can be applied at the surface was built by Geophysical Survey Systems (GSSI), another one built by Hentschel has antennae to measure in frequency ranges of 20 MHz to 800 MHz.
Additionally, a Stepped Frequency Radar System for operation in a helicopter is being developed, it was also already tested on the ground.
Application:
BGR’s ground radar systems are only operated for test purposes. Test areas have been up to now:
- gravel bank Rügen island
- limestone quarry Omya
- farm tracks in the foreland of the Harz mountains
- karst area Wulfbachquellhöhle
- ground test field Fuhrberg
- soil test field Ruthe
- military training area Letzlinger Heide (Poster Bodenradar Letzlinger Heide (PDF, 2 MB))
- deciduous forest Hainich (Poster Georadar Testmessungen zur Bestimmung der Wurzelverteilung im Laubwaldbestand Hainich (PDF, 276 KB))
- coalfire in China (coalfire.org)
Literatur:
Blindow, N et al., 2004. Georadar. In: Knödel, K., Krummel, H. & Lange, G. (Hrsg.), Handbuch zur Erkundung des Untergrundes von Deponien und Altlasten, Band 3: Geophysik, Springer-Verlag, Berlin, Heidelberg.
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