Interpreting complex, three‐dimensional, near‐surface GPR surveys: an integrated modelling and inversion approach

Abstract

With the increasing computational power of modern personal computers, sophisticated modelling and inversion techniques are becoming popular tools for the interpretation of high‐resolution, fully three‐dimensional GPR surveys. In this paper, we present the latest results of ongoing practical research into the development of novel, integrated, finite‐difference time‐domain (FDTD) numerical modelling and linear tomographic inversion methods for the interpretation and analysis of near–surface, 3D GPR data. The proposed approach utilizes the Born approximation solution to the inverse‐scattering problem and a truncated singular value decomposition (TSVD) to create the final, inverted reconstructions. A three‐dimensional, full‐field, O(2,4) accurate FDTD modelling scheme is used to generate the numerical‐based Green’s functions and incident fields for the inversion. As such, accurate antenna sources (including the influence of shields) and near‐field air/ground interface effects are inherently included in the inversion formulation. The performance of this integrated method is evaluated via a simulated, 3D, forensic‐based, test‐case example (a 900 MHz survey over a clandestine human burial target) including coherent noise from near‐surface clutter. Although the example is simplistic, the results show that the scheme works well, despite some assumptions in the inversion methodology. As such, useful information can be gained on the true form, depth, location and spatial interrelationships of the buried features and, therefore, improved interpretations can be obtained in a three‐dimensional context.

Experimental forensic scenes for the characterization of ground-penetrating radar wave response

“…Moreover, FDTD modeling is highly recommended when the interpretation of GPR data is not clear. Other authors have probed how the use of numerical FDTD modeling becomes an effective tool for improving the analysis and interpretation of GPR data [29]. In this study, more realistic synthetic models were constructed with the accurate geometric data obtained with photogrammetry.…”

“…For synthetic plastic (PVC) and bone materials, parameters were assumed from the literature ( [28] and [29], respectively). In the case of a sandy-clay medium (backfill 1), relative permittivity was estimated using the radar wave velocity calculated, and the conductivity was set according to the soil analysis provided.…”

A New Approach to the Detection of Vertebrate Skeletons by Ground Penetrating Radars: An Example from the Ica Desert Fossil-Lagerstätte

“…Classical methods of analysis of near-surface radar data generally rely on the visual inspection and interpretation of reflection profiles (e.g., 1 ) and sometimes on the inverse modelling of the acquired data (e.g., 2 ). These methods have been successfully applied in several fields, from archaeological research to civil engineering, to detect relatively large structures buried at shallow depth, but suffer from severe limitations when the target has a thickness below the Ricker or Rayleigh estimates of the GPR antenna vertical resolution.…”

Detection of karst caves during tunnel construction using ground‐penetrating radar and advanced drilling: A case study in Guangxi Province, China

“…Scholars have proposed many imaging techniques, such as full‐waveform inversion, tomography and migration imaging to map the detected target (Fletcher et al ., 2009; Lavoué et al ., 2014; Bradford, 2015; Salcedo et al ., 2020). For large and complex karst caves, however, those GPR imaging techniques are still limited to theoretical analysis and difficult to be used in engineering practice (Millington et al ., 2011). Due to the space limitation in tunnels, it is difficult to obtain a complete reflection signal for the detected target.…”