Digital expansion: ADS-B and MLAT/WAM

Present and future of aeronautical technology.
SEPTEMBER, 30 / 2019 / 5 MINUTES
Фото вышки в Örnsköldsvik
Today, secondary radar remains one of the most widely used air navigation aids in the world, however, the update of the global ATM system continues, and new ADS-B and multilateration (MLAT/WAM) technologies occupy a larger niche gradually.
Airborne ADS-B 1090ES transponders have been put on new commercial airliners for some years now. According to the latest data from Europe, the level of air vehicle's equipment reached 40% in April 2019, which is 22% more than in October 2018. Current mandates in the US and Europe require that by 2020 all commercial airliners be equipped with ADS-B 1090ES Out equipment. Below is a visual graphic illustrating these requirements in different countries of the world.
Green — RTCA / D260; RTCA / DO-260A; Blue — RTCA / DO-260B.
Some countries, such as Australia, have already required the ADS-B onboard installation in accordance with DO-260A. According to the European mandate, the time line for switching to automatic dependent surveillance is determined until June 7, 2020. The US FAA gives time until January 1, 2020. As for the ground-based infrastructure implementation, different countries have achieved different results. Let us focus on some of them.
In the USA, the ADS-B stations network covers almost the entire territory of the country. As Sky review had already wrote, two data links are used there: UAT (for general aviation and up to 18,000 feet); 1090ES at all heights.
In some regions of the United States, the FAA has also deployed MLAT/WAM: in particular, at several airports in the Colorado Mountains; the system also works in Juneau (Alaska); in Charlotte (North Carolina).
In Europe, ADS-B, as well as in the USA, has been introduced for several years. The most current coverage map is as follows:
It is assumed that ADS-B will, if necessary, work "in conjunction" with existing independent MLAT/WAM and secondary radars, since the airspace of Europe is characterized by a high traffic density. This will add an extra "layer of redundancy" and improve safety.
SESAR Deployment Manager
Detailed information on the status of the ADS-B introduction in Europe can be found on the specialized SESAR website.
ADS-B is often combined with MLAT/WAM, in practice. This is because the MLAT/WAM sensors support the operation of the ADS-B 1090ES, and it is also possible to use the MLAT/WAM as a redundancy system that provides greater security and accuracy (MLAT/WAM does not depend on satellite data). Earlier it was reported about 40 systems based on multilateration installed at major European airports. There are also 80 multilateration zones outside the airports. It is noted that multilateration technology can be used as an alternative to secondary radars.
This is one of the first countries that introduced ADS-B 1090ES throughout its territory. The feature of the system is that both ADS-B In/Out transmitters and receivers are used here. Read more about the features of the system in Australia in our material at this link.
WAM system is also deployed in the highlands on the Australian island of Tasmania. At the project appraisal stage, two solutions were compared: one based on secondary radars, the second on multilateration. Preference was given to WAM as a more efficient and cost-effective technology.
New Zealand
A similar situation is with the neighbor of Australia, New Zealand. Most of the country is located in the ADS-B 1090ES surveillance zone, there is WAM in the south.
Coverage Area ADS-B / New Southern Sky / ADS-B in New Zealand
Coverage area of WAM in southern New Zealand / New Southern Sky / ADS-B in New Zeland
In New Zealand, as well as in Australia, they evaluated the experience of implementing two ADS-B data transmission lines in the USA. And they have also came to the conclusion that this solution is redundant and increases the cost of the entire system implementation. The choice was made in favor of a single data line — 1090ES.
China was not an exception. There is also a national ADS-B deployment, and modern MLAT/WAM systems are being introduced at airports. The updated Beijing airport is an example, where a modern MLAT/WAM system was deployed as part of the ground-based traffic control and management system — A-SMGCS.
Other countries where ADS-B 1090ES projects are also being implemented
The list goes on and on. AOPA of the United States has previously identified countries with a ADS-B 1090ES Out mandate. It includes the USA, Australia, Canada, Europe, Hong Kong, Indonesia, Mexico, Singapore, Sri Lanka, Taiwan and Vietnam.
In addition to the classic ADS-B, there is also the space-based one. National Operators of Great Britain (NATS) and Canada (Nav Canada) deployed space-based ADS-B in the North Atlantic and Canada in 2019. The system makes it possible to observe the Atlantic, as well as in remote and geographically complex areas of the world.
Even after the global expansion of ADS-B 1090ES began, multilateration continues to expand and provide additional benefits. The technology has become widespread in the world, both as part of A-SMGCS systems at airports, as well as wide-area solutions (WAM) for entire regions and even countries.
Map with a list of regions of the world where MLAT/WAM / projects were implemented
Experts note that MLAT/WAM systems are able to provide greater accuracy compared to traditional secondary radars.
"Wide-area MLAT/WAMs consist of a large number of small stations. They are able to provide airspace surveillance more efficiently than traditional radars. This solution is superior to secondary radars in both cost and performance",
— says Andrew Getz, representative of Sky guide company (Switzerland). "Wide area multilateration a multitude of antennas instead of radar dishes" BLUEPRINT The 2019 skyguide technology outlook.
"MLAT/WAM sensors are de facto the ADS-B receivers. Therefore, introducing MLAT/WAM, we are simultaneously implementing ADS-B",
— continues Andrew Getz.
National MLAT (WAM) in Namibia. Prior to implementation, there was no radar surveillance in the country. At present, MLAT/WAM provides air navigation throughout the country, the area of about 820 thousand km², which is more than 100 thousand km² more than the area of the whole of France.
MLAT/WAM does not depend on satellite data and is a more autonomous and protected system capable of providing a high level of redundancy and verification of ADS-B 1090ES data. The EU reported plans to create about 20 more WAM zones by 2020, as well as plans to install 30 systems at airports from 2018 to 2020.

Sweden, the UK, Japan, Austria, the USA, Australia, New Zealand, Namibia, Canada, Russia, and the Czech Republic are the countries where the MLAT/WAM projects have been implemented.

In some countries, for example, in Namibia or Sweden, national MLAT/WAM are deployed covering the entire state.

In conclusion, we note that secondary radars, as well as airfield survey locators, continue to operate. However, the global trend towards the introduction of more modern air navigation systems is obvious.
Wide-area MLAT (WAM) in Japan. A network of several MLAT systems is being developed in the country, and will cover most part of the country. The project also includes the introduction of ADS-B 1090ES and is designed until 2024.
More and more countries are starting to deploy ADS-B / multilateration, and one of the drivers of this process is ICAO and the Global Air Navigation Plan (GANP). It is the GANP that has laid down the new principles. And the implementation of them needs modern solutions to ensure a higher rate of updating information, greater accuracy, bandwidth, mobility of systems, as well as their digitalization level.
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