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

Abstract

Abstract 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 × 14 m, using a single‐channel PulseEKKO GPR system equipped with common‐offset (CO) 450 MHz antennas. To satisfy criteria for three‐dimensional migration, the sample density over the grid was 0.05 × 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 × 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‐offset acquisitions will be more readily considered for archaeological GPR investigations. Copyright © 2008 John Wiley & Sons, Ltd.