Three-dimensional, multi-offset ground-penetrating radar imaging of archaeological targets

The efficacy of ground penetrating radar (GPR) methods is inhibited when surveying over a target that is structurally complex and/or hosted within attenuative media. Recent research has documented the ability of certain seismic methods to improve imaging using GPR. For imaging complex targets, three-dimensional acquisition and migration methods are applied. For attenuative sites, signal-to-noise ratio (SNR) may be boosted on acquisition of multi-offset data. We present results from an integrated three-dimensional multi-offset survey over a Romano-British villa at Groundwell Ridge, near Swindon, UK. Data were acquired within a grid of dimension 21 m x 14 m, using a single-channel PulseEKKO GPR system equipped with common-off set (CO) 450 MHz antennas. To satisfy criteria for three-dimensional migration, the sample density over the grid was 0.05 x 0.05 m(2). A smaller grid of three-dimensional multi-offset data was acquired, with fold-of-cover 2200%, targeting a low SNR section of data. The spatial resolution and SNR in the resulting images of the target are greatly improved compared with data acquired using a more conventional survey method. However, this improvement may not be justified by the greatly increased (some 10 times) fieldwork effort required to obtain three-dimensional multi-offset data. We therefore investigate a means of improving the efficiency of three-dimensional GPR surveying by applying a simple trace interpolation method to recover three-dimensional acquisition criteria. This trial suggests that, at this site, three-dimensional data can be simulated from a grid of pseudo-three-dimensional data, sampled at 0.05 x 0.25 m(2). In this way, high quality images of an archaeological target can be obtained with minimal increase to survey effort. We hope that, on the basis of this work, three-dimensional and multi-off set acquisitions will be more readily considered for archaeological GPR investigations. Copyright (C) 2008 John Wiley & Sons, Ltd.