A Coarse-to-Fine DLG and TLS Data Registration Method

Terrestrial laser scanning (TLS) is an efficient tool to capture the point cloud for facade modeling. However, it is not easy to obtain the position by Global Navigation Satellite System (GNSS) as occluded by high buildings, which would lead to a problem in orienting the TLS data to a target coordinate system. In this article, we propose a coarse-to-fine registration method for reliably orienting the TLS data using a digital line graph (DLG). The orientation is completed by horizontal plane registration and elevation registration parts. The proposed method is composed of five steps: 1) using the proposed method to extract the corner points from the building outline of DLG; 2) using the proposed method based on RANSAC algorithm to extract the corner points and the facade point clouds of the TLS data; 3) coarse alignment of the two extracted sets of corner points using four-point congruent set algorithm; 4) fine registration by 2D-ICP algorithm; and 5) completing elevation registration using elevation control points. Three datasets are employed to perform the experiments, and the results confirm that the proposed method is reliable and efficient in achieving the registration of DLG and TLS data. After comparing with two other typical registration methods, it is found that the proposed method performs better.