Close photogrammetry and laser scanning using a mobile mapping system for the high detailed survey of a high density urban area

The realization of an urban underground is a key issue for the development of any city, and it has to regard all problems linked to the project phase and the connections with many other works like railways, bus-lines and, specially for an ancient city like Bologna, historical buildings. For these reasons the Municipality of Bologna has committed the ultimate design of the underground line with a high standard level of precision; this aspect forces the Project Group to choose a survey method that has to be both accurate and not too expensive. In order to achieve a precise high resolution survey in a short time, a Mobile Mapping System vehicle has been used. The Road-Scanner” system is equipped with 2GPS+IMU sensors for navigation (Applanix POSLV), four cameras for close range photogrammetric survey and a Laser scanner FARO LS880. Moreover, in order to obtain good and homogeneous results a geodetic network (performed using GPS and topographic survey) has been made in some area along the track. In this contribute the authors, starting from the municipality requirements, describe all the performed work and analyze the obtained results.