Abstract text

A method of triangulating aircraft transponder signals using a number of receivers connected to a central station over communication links includes applying at least one logic rule at each receiver to incoming transponder signals to filter redundant transponder signals, time-stamping filtered transponder signals, and transmitting time-stamped transponder signals to the central station. Logic rules include at least one of altitude filtering, Mode S, Mode A/C code filtering, and change filtering. Replies are accepted when a change in state is indicated, such that the only those replies indicating a change in state are time-stamped and sent to the central server.