I. Introduction
The enormous interest of people in Unmanned Aerial Vehicles (UAVs) - also known as drones - is only a small example of the commercial impact that these aircraft will have in our industries in next years. The UAVs' global market is expected to reach US$ 2 billion by 2022 [1]. New technologies are expected to allow the use of aerial vehicles to cargo transportation [2] [4], agriculture support [5] [6], mapping [7] [8], pest control [9] [10], surveillance [11], [12], inspection [13] [14], entertainment [15] [16], and so on.