Ground penetrating radar (GPR)
GPR systems comprise of a configuration/data acquisition unit, single or multi-frequency antenna (or array of antennas), and a wheeled cart or survey wheel fixed with an odometer or GPS.
GPR is used to transmit a continuous electromagnetic pulse or wave of energy into the ground and record reflections of that energy following its interaction with the objects and layers below the surface. Reflections of the radar pulse are recorded on return to the surface by the GPR system, and the strength of these reflections is proportional to the conductive and dielectric properties of the layers and objects present below the surface.
Data is typically acquired along parallel transects, 0.1m or 0.25m apart, and recorded as a function of 2-way travel time, representing the elapsed time for the energy wave to travel from the GPR system to reflector and back to the surface. On completion of fieldwork the acquired radargrams are processed and then combined into a 3-D volume, from which time slices are generated for display of significant reflections recorded below the surface.
TARGET has undertaken GPR surveys at the interior of existing buildings, on urban sites and agricultural land, successfully locating buried remains of
- Former cemeteries & burials
- Roman villa sites, castles & tower house remains
- Gallo-Roman temples
- Early church foundations
- Medieval buildings