The Impact of Spatial Sampling and Migration on the Interpretation of Complex Archaeological Ground‐penetrating Radar Data

Abstract

In this paper, the impact of spatial sample density and three-dimensional migration processing on the interpretation of archaeological ground-penetrating radar (GPR) data is assessed. First, the question of how to determine the sample interval required to take full advantage of the spatial resolution capabilities of GPR without oversampling is addressed. To this end, we transform a test profile into the frequency-wavenumber (f-k) domain and estimate the required sample interval from the wavenumber values. For the presented data set, collected at the Roman town Ammaia (Portugal), this resulted in a transect spacing approximately three times the distance prescribed by the λ min /4 criterion (where λ min is the minimum observed wavelength). Second, the effect of three-dimensional migration is assessed. The data set, sampled as prescribed by the analysis of the f-k plot, is migrated with two-and three-dimensional phase-shift algorithms, and the migrated results are compared with non-migrated data. It is shown that certain subtle features are better resolved by three-dimensional migration. Third, it is investigated whether three-dimensional migration following the application of an interpolation algorithm such as Delaunay triangulation or interpolation based on τ-p transform, can further relax spatial sampling requirements. For the GPR data shown in this article, it is demonstrated that interpolation and three-dimensional migration of slightly aliased data, collected with a transect spacing equal to five times the outcome of the λ min /4 criterion, still allow a faithful reconstruction of the original, non-aliased time-slices. Figure 5. Energy time-slices from between 31 and 32 ns, showing details from areas 1A and 1B, surveyed with a 0.05 m × 0.05 m grid spacing in east west and north south directions, respectively: (a and b) data after three-dimensional phase-shift migration; (c and d) data after two-dimensional phase-shift migration in in-line direction; (e and f) Unmigrated data. The large arrows show the direction of the survey lines. The numbers are explained in the text.

Ground-penetrating radar survey at Falerii Novi: a new approach to the study of Roman cities

“…These stripes were suppressed by calculating the average of the data recorded by each channel within a swath and then equalising these average values. Subsequently, migration (Verdonck et al 2015) improved lateral resolution, as illustrated in Figure 3.…”

Detection of Buried Roman Wall Remains in Ground‐penetrating Radar Data using Template Matching

“…A robotic total station continuously tracked the prism on the GPR platform. We used a transect spacing of ~0.125 m, resulting in slight aliasing compared to the theoretically required transect spacing of 0.075 m, obtained through the transformation of representative profiles to the frequency‐wavenumber domain (Verdonck et al ., ). After dewow and time zero alignment, the same gain function was applied to all traces to enhance later arrivals and preserve relative amplitudes.…”

Ballistic Ground Penetrating Radar Equipment for Blast-Exposed Security Applications

“…While typically analysed in the 2D domain, the use of 3D imaging techniques produces more realistic images of the subsurface, allowing for a more accurate location and for a 3D reconstruction not only of the buried targets, but also of the surrounding environment. The price to pay is a very high accuracy during acquisition, particularly in data density and regularity, to prevent possible artefacts resulting from the interpolation between the data samples [53]. Given the framework of application, the principal sources logistical obstacles, ground topography or poorly conducted surveys can be considered as the main sources of acquisition errors.…”