Multilateration - digital air traffic surveillance technology

When it comes to aviation, we all vividly represent the sky, aircraft, airports, travel. And rarely anyone thinks about the complex system created for the regulation of air traffic. The concept of the International Civil Aviation Organization CNS / ATM (Communication, Navigation, Surveillance / Air Traffic Management) predicts full digitalization of air traffic in the near future.

Today we will talk about one of the most modern means of monitoring air traffic - multi-position surveillance systems (MPSS in Russia, MLAT, WAM in the world), which are based on the principle of multilateration.

The technology of multilateration appeared about 20 years ago at about the same time as automatic dependent surveillance (ADS-B), which by the standards of the conservative industry quite a bit. And during these 20 years, MSSP has come a long way from a new technology to one of the main assets in today's and future air navigation systems.

MSS is a secondary radar in which the coordinates of targets are measured using the difference-distance-measuring method through a network of geographically-distributed stations (ADS-B, AFN-B satellite-dependent observation sensors).

How it works?

As with any secondary radar, the ground interrogator emits a request, the responder on board the aircraft receives the request and generates a response, which is accepted by the system. This answer is used to measure the position of the aircraft, and it also transmits additional information: first of all, height and identification. But if a traditional locator measures the distance and direction to the aircraft, for which a massive rotating antenna with a narrow beam is used, the MPSS stations receive signals from targets from all directions, and the coordinates of the aircraft are calculated from the delay of the signal arrival time to different stations.

For this method of measuring coordinates, different names are used. Difference-ranging method is one of these names. The term "multilateration" is widely used. Actually, MSS is often called multilateration systems, or MLAT. The measurement method itself is also called the English abbreviation TDOA, which means time difference of arrival - the difference in arrival time, or hyperbolic positioning, because geometrically the location of points corresponding to a certain arrival time difference for any two stations is the hyperbola, and the target coordinates are their intersections .

Thus, MSS is a secondary radar facility. But there are a number of advantages over traditional radars. First of all, it is a higher rate of information update (1 second) and higher accuracy. This is an opportunity to create a surveillance zone where it is needed - at low altitudes, in mountainous areas, and so on. This is an opportunity to place equipment that is compact and consumes no more than a light bulb energy on the existing infrastructure, without capital construction.

In Russia, the first integrated multi-point surveillance system, which simultaneously performs the functions of an aerodrome and wide-area surveillance facility, appeared in 2016. The system supports all surveillance modes, in particular, the AZN-B mode 1090 ES, which is recommended by ICAO as a single standard for the entire global airspace, and is also declared as protected from cyber attacks.

Promise to introduce it in the near future. And the first airport to be equipped with such a system is Pulkovo, St. Petersburg.


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