Uav photogrammetry for cultural heritage preservation modeling and mapping Venetian Walls of Bergamo

In July 2017, the system of Bergamo City Walls was registered in the UNESCO World Heritage List, together with other Venetian fortresses in Italy, Croatia and Montenegro. This important historical document needs continuous care and caution in order to be preserved complete, despite the continuous atmospheric and anthropic attacks, giving rise to dangerous deterioration processes on the artefact. The UAV photogrammetry is a suitable surveying method for such an extended system, able to collect all the geometrical, material and deterioration information needed for an effective maintenance program, also quick enough to allow for repeated monitoring of the entire wall circuit. This paper presents the UAV survey campaign planned, and partially already completed, in order to test the methodological choices and solve all the operational difficulties to use drones in an urban environment, mainly because short distance shooting of nearly vertical surfaces was required.