ACCURACY ASSESSMENT OF A CANAL-TUNNEL 3D MODEL BY COMPARING PHOTOGRAMMETRY AND LASERSCANNING RECORDING TECHNIQUES
Other literature type
(issn: 2194-9034, eissn: 2194-9034)
With recent developments in the field of technology and computer science, conventional methods are being supplanted by laser scanning
and digital photogrammetry. These two different surveying techniques generate 3-D models of real world objects or structures. In this
paper, we consider the application of terrestrial Laser scanning (TLS) and photogrammetry to the surveying of canal tunnels. The
inspection of such structures requires time, safe access, specific processing and professional operators. Therefore, a French partnership
proposes to develop a dedicated equipment based on image processing for visual inspection of canal tunnels. A 3D model of the vault
and side walls of the tunnel is constructed from images recorded onboard a boat moving inside the tunnel. To assess the accuracy of
this photogrammetric model (PM), a reference model is build using static TLS. We here address the problem comparing the resulting
point clouds. Difficulties arise because of the highly differentiated acquisition processes, which result in very different point densities.
We propose a new tool, designed to compare differences between pairs of point cloud or surfaces (triangulated meshes). Moreover,
dealing with huge datasets requires the implementation of appropriate structures and algorithms. Several techniques are presented :
point-to-point, cloud-to-cloud and cloud-to-mesh. In addition farthest point resampling, octree structure and Hausdorff distance are
adopted and described. Experimental results are shown for a 475 m long canal tunnel located in France.