The Viterbi algorithm as an approach for incorporating spatial information into air/ground interface inference in GPR data

Abstract

Rough surfaces present an impediment to the detection of buried threats with ground penetrating radar (GPR). Besides introducing artifacts in the sub-surface due to rough scattering, very rough or uneven surfaces can make inference of the location of the ground response from GPR data difficult. Since many algorithms rely on the accurate localization of the air/ground interface, mistakes in ground location inference can cause significant increases in false alarm rates. Many different approaches to localizing the ground in a particular A-scan have been proposed, but sharing information across multiple A-scans to form a realistic, smoothly varying ground response over many spatial locations is a difficult problem that often requires computationally expensive approaches for adequate solutions. In this work we present an application of the well-known Viterbi algorithm for accurate localization of the air/ground interface based on hypothesized locations from multiple nearby A-scans. Our implementation of the Viterbi algorithm enables principled incorporation of prior information into the ground tracking framework, and provides a solution capable of adapting computational complexity to the severity of the ground localization problem. Furthermore, the Viterbi algorithm can act as a meta-algorithm, allowing the use of different A-scan based ground detectors as input, for example. This work illustrates how the Viterbi algorithm can be incorporated into pre-screening algorithms to provide improved target detection rates at lower false alarm rates.