Autonomous flying vehicles represent an innovative solution for various service robotics scenarios. In particular, the capability of acting in formation opens to new opportunities in a multiplicity of different fields. One of the many advantages of having multiple Unmanned Aerial Vehicles (UAVs) operating collaboratively is the possibility to sense the relative distances from an object and localize it with respect to their position in space. The case analyzed in this document consists of a reference body, be it terrestrial or aerial, autonomous or human-controlled, that operates in a GNSS-denied environment: computing its position at all times is a fundamental challenge, that is overcome thanks to the information exchanged with a fleet of drones.