Enhanced target imaging in 3D using GPR data from orthogonal profile lines

Abstract

Continuing improvements in computer technology have made 3-D imaging a standard GPR interpretation technique. The most common data collection methodology for 3-D imaging involves collection of data along parallel profile lines. The data are then often migrated and concatenated into a 3-D file. A 3-D image generated from the file is manipulated to detect linear and finite-size targets. The detection of linear and finite-size targets can be enhanced by creating images generated from data collected along orthogonal profile lines. The fact that the minimum angle formed between the long axis of a linear target and one of the orthogonal profile lines is 45 degrees enhances the detection of a linear target because in at least one profile line direction the reflection from the linear target will form the familiar hyperbola and a series of hyperbolas concatenated from parallel profile lines are readily observed in the 3-D image. Perhaps the most beneficial aspect of using bi-directional data is the ability to perform spatial filtering operators to improve detection of linear targets. Background removal filters applied to parallel profile line data will generally erase reflections from pipes or rebar that trend parallel to the direction of the profile lines. Comparisons of the data visualization capabilities between one-direction and orthogonal profile line data collected on reinforced concrete and on a buried pipe test site clearly show the advantages of imaging using orthogonal profile line data on both small and large scales.