Comparing classifier effectiveness

The classification and even, if possible, identification of any object or target under observation unambiguously at a distance and in such short times that a decision and an `adapted' reaction are possible was, is and will be a most important task in the military and also security domains. There is an ongoing effort in many countries all over the world, and of course also in NATO, to improve the existing solutions. One approach, the obvious one, is the idea to allow any object entering observed areas to identify itself actively on request. Such systems have been installed for many years in the military domain and are called `Q&A' systems or `identification friend or foe' (IFF) systems. For air targets, and if radar is used as the sensor system, aircraft have been equipped for many years with systems like Mark X or Mark XII in different modes which were able to answer an interrogating pulse from the observer with a predefined code revealing, in addition to other information, its identity. Systems like that are also used in the civilian air traffic control (ATC) and because they support the interrogator they are called `cooperative identification systems'. However, they show some important drawbacks.