Various approaches have been suggested for velocity analysis on man-made structures, such as the evaluation of reflection amplitudes and diffraction hyperbolas, calibration using cores and multi-offset analysis with different antenna types and acquisition setups. As none of these methods can be considered best under all circumstances, a choice has to be made for each given problem. Feasibility, cost and accuracy have to be considered when making this choice. This paper describes the benefits and limits of multi-offset velocity analysis using two ground/object-coupled 1.5 GHz antennas (GSSI, Model 5100). One of these antennas is off-the-shelf, the other one was purpose-built in order to increase the possible range of offsets. Important factors such as depth of penetration, vertical resolution, offset range and the number of scans required are discussed using datasets acquired on-site and in the laboratory. The emphasis is on asphalt pavements and concrete structures. This paper aims to provide support for decisions on whether this approach is suitable for a given problem.
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