Ellipse Inversion Model for Estimating the Orientation and Radius of Pipes From GPR Image

Ground penetrating radar (GPR) has been widely used as a nondestructive tool to image the subsurface. When the GPR's detecting direction is perpendicular to the orientation of a buried pipeline, a hyperbolic feature would be formed on the GPR B-scan image, which could then be identified and fitted to estimate the target pipeline and the permittivity of the area. However, in real-world applications, the orientation of pipelines on the existing pipeline map could be inaccurate, and it is hard to ensure that the moving direction of GPR is actually perpendicular to the underground pipeline. In this article, a novel model is proposed to estimate the orientation and radius of the pipeline from the GPR B-scan image, provided the permittivity of the underground medium. The model consists of the following two parts: GPR B-scan image processing and ellipse iterative inversion algorithm (EIIA). First, the GPR B-scan image is processed with the downward-opening point set extracted. The obtained point set is then iteratively inverted to the elliptical cross-section of the buried pipeline, which is caused by the angle between the GPR's detecting direction and the pipeline's orientation. By minimizing the sum of the algebraic distances from the extracted point set to the inverted ellipse, the most likely pipeline's orientation and radius are determined. Experiments on real-world datasets are conducted and analyzed, of which the results demonstrate the effectiveness of the proposed model.