Automated three‐dimensional georadar acquisition

Abstract

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 three-dimensional (3-D) georadar data. This surveying system provides complete coordinate information with high accuracy. Quasi-continuous georadar and coordinate data are recorded simultaneously as the georadar antennas are transported across survey areas. Before the georadar data can be subjected to advanced processing procedures they must be transferred on to a regular grid. Therefore, post-acquisition processing begins with an automated analysis of the stored coordinates to determine the grid orientation that best matches the original positions of the recorded data: a two-dimensional Fourier transform technique has been designed for this task. By summing all data recorded within a specified area of a grid point, a relatively high number of vertical stacks and a correspondingly high signal-to-noise ratio are achieved. The combined georadar-laser theodolite 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. With the new system, 3-D georadar acquisition is speeded up relative to standard procedures by a factor of 5 to 10.