## 1 Introduction  
The Italian infrastructures network (roads, highways, and railways) represents a connection system of outstanding importance for social and economic life of the whole country: Actually, the total length of road network is about 59,000 km and includes 1300 tunnels, 7000 overpasses, and 17,000 bridges. Transportation infrastructure plays a significant role in the success of every nation's economy: In particular, road transport is the primary means of national transportation, so maintaining a reliable and durable road infrastructure is essential to economic growth and social development. Moreover, Italy is a country strongly affected by natural hazards, such as landslides [1], which often are cause of deaths, injured and physical damage to private and public properties. Among these, slow-moving landslides, generating deformation, cracks and local failures to road surface, are responsible for considerable economic losses [2]. For this reason, an effective monitoring system, performed by using an onsite network of sensors and instruments, should be required during the exercise phase to support control and management activities by owners and authorities. Actually, monitoring and control of the Italian infrastructures is instead demanded to technicians and maintenance teams who detect, by means of visual control, anomalies and failures which could represent a critical condition for users. Such approach, besides representing a relevant rate of owner's annual budget, could not be effective because of the long time-lapse between in situ data collection and information transfer to the operating center. Indeed, a complete monitoring system should include also accelerometers, levelling, total station surveying, laser scanning, GNSS (Global Navigation Satellite System) technologies to control deformation of structures, wireless sensors to detect deterioration of materials, and gauges to monitor stresses of structural elements [3; 4; 5]. However, it is important to highlight that punctual measurements, carried out at specific points of interest, even though they are without any reasonable doubt accurate and reliable, could represent a limited and only partial information to fully characterize and analyze a potential infrastructure damage and can be highly expensive if a high density of measurements suitable for wide-scale infrastructure monitoring is required. Recently, remote controlled Unmanned Aerial Vehicles (UAV) have been widely accepted among the scientific community as platforms for implementing monitoring and inspection procedures. Equipped with high definition photo and video cameras, UAV systems can fly autonomously following a preprogrammed flight path or remotely controlled by a navigator. They provide a safe method for remotely performing visual inspections and inventorying of damage and failures along linear infrastructures: Furthermore, the possibility of geo-referencing of images suggests an efficient displacement detection of structures based on photogrammetric methods. In spite of all benefits, UAVs have some essential limitations, due to short flight time, high sensitivity to changes in the weather conditions, unexpected flight situations (occurrence of obstacle, failures of GPS signal). The need of an effective and quasi real time approach for monitoring of these man-made infrastructures, finds in the application of modern remote sensing techniques a valid response with a good cost/benefit ratio. Satellite-based monitoring systems, based on the use of radar images, may offer a feasible source of independent information products to support infrastructures health assessments. As a matter of fact, such technique can be effectively used to detect surface movements both of infrastructures and surrounding areas [6].