Survey by Airborne Laser Scanner of open large structure: A case study of Pompeii Amphitheatre

The purpose of this paper is to show the potential of Airborne Laser Scanner (ALS) in the survey of large and open structures in the Cultural Heritage field. Nowadays, this technology is becoming spread in the field of Cultural Heritage thanks to the possibility to obtain a large number of points in a short time. In fact, the latest generation of ALS sensors are able to acquire up to several million measurements per second and to generate an elevated point density. In addition, if this sensor is combined with digital camera, it is possible to obtain even RGB colour information. In this paper are described the features, methods and techniques for acquisition by ALS system. In particular, it is presented a wide analyse of the three dataset (calibration, laser distance measurements and Position-Orientation System data). The assembly of these datasets allows obtaining the correct georeferncing of the point clouds. A case study of a survey carried out by ALS system on the archaeological site of Pompeii (Italy) is presented. In this case, all the steps necessary to realize the survey are described (planning, acquisition and post-processing task). Also, starting from the point clouds, in CAD environment a classic representation (in a suitable scale) of Roman amphitheatre is showed.