Automatic Registration of Terrestrial Laser Scanner Data via Imagery

The registration of point clouds forms the first task associated with building 3D models from laser scanner data in cases where multiple scans are required for complete coverage of the scene or object being recorded. This paper presents an automatic registration method for terrestrial laser scanner (TLS) data in which the transformation parameters of one data set with respect to another are determined via 3D similarity transformation. Coded targets placed on the object are imaged using a calibrated digital camera, rigidly attached to the laser scanner. These coded targets are identified, measured and labelled automatically in the imagery from each TLS station. The spatial position and orientation of the camera within the TLS coordinate system, along with the wellknown collinearity equation of close range photogrammetry, are then used to automatically find the targets in the laser scanner point clouds. Finally, the identified coded targets in the scan data serve as common or ‘tie’ points for the 3D similarity transformation which registers one point cloud with another overlapping data set. The proposed method provides a simultaneous registration of overlapping TLS point clouds. Test results obtained with the approach are presented to highlight its practicability and accuracy.