A Numerical Algorithm for Integrating Digital Close Range Photogrammetry and 3d Laser-Scanning

We present an original algorithm for integrating digital photogrammetry and laser-scanning in which the block adjustment of the scanner point clouds and of the bundles of image spatial rays is carried out in the same reference frame. In particular, by using a single digital image, the proposed algorithm associates with a generic point in the image plane of a photogrammetric image its 3D coordinates evaluated by means of the point cloud generated by the laser scanner. The case study presented in the paper is related to the survey of an entrance portal of the Benedectine Abbey of Montecassino, a famous monument located in the center of Italy. The point cloud has been acquired by an Optech laser scanner and the digital image by means of a suitably calibrated low cost digital camera. After an accurate illustration of the algorithm the main results of the precision test are presented and discussed.