The provision of air traffic services is subject to a reliable and accurate knowledge of the position of the aircraft. The radar information necessary for air traffic control is provided by primary (traditional) and secondary radars. Further information is provided by multilateration systems and ADS-B systems. Along with the information from their own devices, ANS CR also process radar signals received from foreign partners.
A primary radar antenna emits periodically its electromagnetic energy which, when reflected from an object, is processed by a receiver. The position of the target is calculated according to the current antenna position and time from sending a signal until its reflection is received.
A secondary radar is used to determine the position of an active transponder-equipped aircraft, with the help of which you can determine not only the position of the aircraft, but also other information (aircraft identification, altitude and in the case of a radar operating in the S mode also other information).
ANS CR obtains the necessary data from radars located at the airports in Prague, Brno, and Ostrava and in addition from radars on the Písek and Buchtův kopec hills. From abroad we get data from Germany and Slovakia.
The multilateration (MLAT) technology uses the principle of S mode message reception with multiple receiving stations. The location of stations is accurately known, and the objective position is calculated from the difference in the time of signal reception at these stations. The operating performance of MLAT in terms of accuracy and content of all other data from the responses (code number of the aircraft, flight level) is almost identical with the performance of the secondary radar.
Multilateration systems can be installed in two configurations depending on the use, either for regional air traffic control or airport applications such as A-SMGCS element (airport surveillance system). The receiving station may be an element of the ADS-B system (Automatic Dependent Surveillance - Broadcast).
Control of the aircraft "on the ground"
For traffic control in the operational areas of the airport information from the mobile radar SMR and from the Multilateration system, P3D is used. Information from these devices are transmitted to the device A-SMGCS (Advanced Surface Movement Guidance and Control System), which is used by the air traffic controllers as the main displaying system for tracking and identification of aircrafts and ground vehicles moving in the operational areas of the airport.
In addition to the basic monitoring function, the system installed at ANS CR also has the warning function. The system draws attention to possible collisions of aircraft and other vehicles on the airport surface.