Registration of terrestrial laser scanner data using imagery

At the present time there is a considerable amount of development interest in the use of terrestrial laser scanner (TLS) data for 3D reconstruction and modelling in the fields of heritage recording and plant documentation. TLS technology produces point clouds of very high density in a very short time. When surveying an object of complex geometry, multiple scans are typically required to generate an occlusion-free 3D model. The principal task associated with building 3D models from laser scanner data in such cases is to transform the scan data from the sensor's local coordinate system into a uniform Cartesian reference datum. This is necessary in order to join the multiple point clouds. This paper presents a registration procedure for TLS data whereby the exterior orientations of the TLS stations are determined via photogrammetry. The images from a digital camera mounted on top of the laser scanner are used first to relatively orient the network of images and then transfer this orientation to the TLS stations to provide exterior orientation and thus a one-step registration of the point clouds from each scanner position. Test results obtained with the proposed approach are presented to highlight its efficiency and accuracy.