Combining Photogrammetric And Bathymetric Data To Build A 3d Model Of A Canal Tunnel

This paper introduces an original method for modelling in 3D the full tube (both vault and canal) of navigable tunnels using data acquired dynamically from a boat. The recording system is composed of cameras that provide images of the vault and a multibeam echo sounder that acquires 3D profiles underwater. Reconstructing partially submerged structures, in a confined environment where no global positioning system signal is available, is challenging. The method exploits the capabilities of photogrammetry, not only to reconstruct the tunnel vault, but also to estimate the trajectory of the vessel, which is necessary to rearrange sonar profiles and form the 3D model of the canal. The comparison of a model reconstructed from in situ dynamic acquisitions with a reference one, obtained from static laser and sonar acquisitions, shows that the accuracy is of the order of a centimetre for the vault, while it is decimetric for underwater features.