Please use this identifier to cite or link to this item: http://hdl.handle.net/10397/61359
Title: Correction of GPR wave velocity at different oblique angles between traverses and alignment of line objects in a common offset antenna setting
Authors: Lai, WWL 
Kind, T
Sham, JFC
Wiggenhauser, H
Keywords: Ground penetrating radar
Hyperbola
Oblique angles
Velocity error
Issue Date: 2016
Publisher: Elsevier
Source: NDT and E international, 2016, v. 82, p. 36-43 How to cite?
Journal: NDT and E international 
Abstract: Estimation of ground penetrating radar's wave velocity in materials is a critical step to accurately estimate depth of embedded line objects in concrete structures, and wetness of material. Errors of velocity are defined as the deviations between the velocities obtained in various oblique angles and those obtained in the traverse normal to the object orientation in a common offset antenna setting. In this paper, we quantified and corrected the errors of such estimation. GPR traverses were designed to travel in various oblique angles θ (90°, 75°, 60° and 45°) relative to the steel bars at 5 cover depths (55 mm, 85 mm, 115 mm, 145 mm and 175 mm). GPR wave velocity at any position within the lateral detection range of steel bars was measured with simple trigonometry in a semi-automated in-house program. It was found that reduction of oblique angles (i.e. θ<90°) causes flatter hyperbolic reflections and the associated errors of velocity can be as much as 30% in the case of an oblique angle 45° before correction. Such errors were corrected after re-scaling the horizontal travel distance with a multiplication factor of sin θ.
URI: http://hdl.handle.net/10397/61359
ISSN: 0963-8695
DOI: 10.1016/j.ndteint.2016.03.003
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