| Explanation
Ground Penetrating Radar (GPR) uses low power radio waves to detect changes in density in the subsurface layers and locate buried objects. Unlike traditional radar, which broadcasts up into the air and uses a parabolic dish to focus the returned waves, GPR uses a small but sensitive receiver which is placed directly against the ground right with the transmitter. The depth that a GPR unit can explore varies depending on the radio frequency used. Low frequencies broadcast deeper but do so with less definition in the resulting image, while high frequencies may only penetrate a meter, but give exact definition. The transmitter is normally set by the manufacturer who will select it based on the purpose for which it will be used. History Originally, GPR was designed for detecting objects buried in ice, but with improvements in receiver technology, the units have been adapted to the more difficult task of detection through the ground. Uses in Archaeology Archaeologists using GPR take measurements at many points around their site, and make an accurate map of their findings to get an overall picture of the subsurface. No individual reading from the unit gives a complete picture and should not necessarily be relied upon. The actual output from the GPR units vary somewhat, from "hyperbola arches" to density levels, depending on the manufacturer of the unit. Cost Sizes of the available GPR units vary from small handheld models to larger models which must be dragged behind the user or towed by a vehicle. Rental costs for a GPR system are around $200 a day. Links |
 GeoModel Inc's SIR-2 GPR unit being dragged across a site
|
