oa Three dimensional georadar acquisition with a real time positioning system

For efficient acquisition of three-dimensional (3-D) subsurface information, quasi-continuous georadar and coordinate data are recorded simultaneously as the georadar antennas are continuously transported across survey areas. A self-tracking laser theodolite with automatic target recognition capabilities has been adapted to serve as a real-time positioning system for the acquisition of the 3-D data. This surveying system provides complete coordinate information with high accuracy. To take advantage of advanced processing procedures the georadar data must be transferred on to a regular grid. A fast two-dimensional Fourier transform technique has been designed for this task. The system has been tested successfully across a number of geological targets in Switzerland. For example, 3-D georadar data were recently collected and processed across a glaciofluvial environment of 25 m x 25 m within a single day. Using the full 3-D information of the data set, channel sediments as well as surface reflections could be clearly identified with the help of time slices.