3D utility mapping using electronically scanned antenna array

Utility mapping using a single-antenna GPR is a timeconsuming operation especially when large areas are to be covered. The data acquisition can be performed much more efficient by using an electronically scanned antenna array. The stepped-frequency 3D GPR that is developed at the Norwegian University of Science and Technology uses a 1 meter wide antenna array that consists of 31 transmit/receive antenna pairs. The main application of the system is utility mapping of streets where the underground consists of a jungle of cables and pipes. The data form the 1 meter wide swath is focused into a 3D image cube using 3D wavenumber migration. By combining several parallel swaths, it is possible to generate underground maps of the whole street at different depths. The radar has successfully been used for mapping of pipes, cables and old tramlines in Trondheim during 2001. The wide bandwidth (100 MHz – 1.6 GHz) gives high enough resolution to map the asphalt thickness and the details of the base layers in addition to the utility lines. In this way, the data from a survey can serve more than one customer. The results from the field tests demonstrate the high user potential of 3D imaging compared to standard 2D GPR profiling.