## 3 UAV Interaction in Mobile and Heterogeneous WSN  
The constant increase of unmanned aerial vehicle (UAV) research programs and relative technologies have allowed to implement systems able to satisfy the requested features so far particularly for surveillance and monitoring operations [16], but many efforts are still needed to develop such systems for civil applications [17], especially in the field of hi-resolution image processing [18] and multimedia services, which represent the main target of this work. In the last few years low-cost micro and mini UAV systems equipped with light-weight geosensors such as video cameras have started to appear in the market [19]. These UAV systems are mostly instrumented with low quality GPS sensors basically for position and flight parameters control. Over the same time period, web-based interactive 3D geo-information solutions have evolved into virtual globe technologies, which have had a significant impact on the geo-spatial industry within a few years. Typical advanced applications are represented by UAV-based augmented monitoring, real-time geo-referencing and integration of video imagery with virtual globe systems. Low cost UAVs are increasingly useful also in remote sensing operations and, in the context of recently funded EU projects, they are potentially capable to revolutionize the multimedia services during particular special events [20]. They can represent a much cheaper alternative to manned vehicles (helicopters and other traditional aircrafts), and they are ideally suited for missions that would be inadvisable for human pilots. Furthermore managing a system of UAVs connected with a terrestrial sensor network can be also a result of interest for their abilities to perform simultaneous coverage of very large areas: UAV platforms can operate as a sink of WSN ground sensor nodes, essentially acting as a mobile gateway or intermediate node, as shown in Figure 1.  
In this context an open field of research is represented by the integration of unmanned aircraft systems (UAS) into advanced multimedia user services. For example, as shown in Figure 2 the capabilities of UAV systems to be integrated with wireless sensor networks and communication devices will open up  
Figure 1: Schematic description of the UAV relay design. new concepts in providing media services, improving also real-time navigation, as well as traditional aircraft related topics such as collision avoidance and formation flight. According to multimedia technology progresses, devices are becoming more and more accessible and related challenges are partly shifting from the technological aspects to the identification of innovative use cases. In this light, the SkyMedia project [20] targets to demonstrate the ability to enhance the level of immersiveness and interactivity of the services provided to four different user categories during an existing Marathon race event. The SkyMedia service should provide advanced services focused onto different target users. Considering the sports event organizer needs, it is possible to deploy different kinds of sensors, both fixed and mobile. For example both mobile sensors placed under the runner shoes or suit and fixed sensors and cameras placed along the marathon path or by the side of the city roads can provide information about the competition itself. Typical information can be represented by the athlete health status, his relative position in the race, shifting from his best previous performance, deviation from the race record and so on. Valuable information could be offered to the runner after the race by summarizing and sharing to him all the gathered data about him obtained from wearable (bio-sensors) and other sensors. In the case of mobile terminal the developed applications can offer an immersive experience by associating recorded data, video stream and 3D models of the location of the event. Users with mobile terminal may also upload information/rich media content (photos/images).