ABSTRACT
The manuscript aims at providing the reader with the awareness about the available technologies and methods for surveying and monitoring the territory, intended in its comprehensive meaning including both the built heritage and the natural environment. An accurate and reliable description of the territory is provided by high density technologies such as laser scanning and photogrammetry. These technologies enable a wide range of analysis and investigations thanks to the generation of high resolution 3D models. Nowadays, the most adopted strategy lies in combining both methods in an integrated approach that allows achieving the most complete results, characterized by the high quality of both the geometric and colorimetric contents. The mentioned technologies are based on cost-effective sensors such as the laser scanner, increasingly available at affordable prices, and optical cameras, among the most diffused devices. They can be used in ground-based operative mode, often with a tripod or similar installation systems, and also mounted on board of unmanned aerial vehicles (namely drones). The last option, being based on flying platforms, has many benefits: it enables applications at a larger spatial scale, it is suitable for any condition that is unsafe for the surveyors and it is a complementary approach for the areas that cannot be easily seen from a terrestrial point of view. The manuscript briefly describes the principles of such technologies and then shows their usefulness in emergency management by using examples organized depending on the time scale. The most suitable approach to be used for data collection and processing as well as for exploiting the final 3D model, strongly depends on the specific phase of the emergency management that is faced: before an event occurs, the 3D model is fundamental for fostering a preventive approach in the territory management; after an emergency occurs, the geospatial information as given by the 3D model is essential to properly and promptly plan rescues and interventions. With this mind-set, two case studies related to seismic risk are shown, with the intent to transfer the approach to the reader who could apply it to a number of different types of risk and emergency scenarios.
