As I already wrote, in the word “aeronautics” there is “nautical”. This is no coincidence. So much so that for several years the world of aviation has been developing a concept similar to maritime AIS : ADS-B. I also would not be able to say which of the two is the first , it doesn't matter !
As the news that concerns us is a little flat these days – normal in July – I became interested in air navigation when I discovered an iPad application, which I will talk about a little further down.
ADS-B, Automatic Dependent Surveillance-Broadcast, which can be translated as “Diffusion Dependent Automatic Surveillance” is generally based on the same principle as AIS. Only the technical means differ.
ADS-B is considered the successor to radar by the United States Aeronautics Administration (FAA). It uses positioning provided by the GPS system to determine and share precise information regarding the position and flight characteristics of an aircraft, broacasting this information to surrounding aircraft equipped with the same system.
The principle
Planes communicate automatically with each other and with ground stations. A bord, the ADS-B system transmits information : airplane type and identification, location, heading, horizontal and vertical speeds, path. Accompanied by a mapping GPS, this instrument allows pilots to view the aircraft around them and to be seen by them, as well as by the screens of the ground control stations.
In addition to classic position and navigation data, ADS-B can also provide terrain and obstacle information, display traffic information and, within certain limits, dangerous weather conditions to avoid.
The system
There are three ADS-B communications systems available :
- 1090ES = 1090 MHz Extended Squitter
- UAT = Universal Access Transceiver
- VDL-4 = VHF Data Link Mode 4
March, the 1090ES is an extension of existing Mode S radar transponder on board commercial airplanes working 1090 MHz. On aircraft equipped, these transponders already make it possible to send and receive messages used by air traffic control on the ground (TCAS). A simple modification of the equipment allows them to send messages (ADS-B OUT) and receive them (ADS-B IN). On the ground, ADS-B information can be received either by a Mode S radar, either by a simple omnidirectional antenna, much less expensive. As almost all commercial aircraft are already equipped with TCAS, 1090ES is a relatively inexpensive solution for them. It is not the same for other planes, especially small private planes, for which ADS-B 1090ES installation is very expensive.
The’UAT is better suited to private aviation. It is a transceiver designed specifically for ADS-B which works 978 MHz. UAT is a specifically American system. UAT conceptors hope that the cost of this equipment will soon be affordable enough for it to be installed on all private aircraft.
March, the VDL mode 4 is both a means of surveillance and communication, operating in the aeronautical VHF band for navigation equipment (108-118 MHz). The VDL-4 allows ADS-B surveillance and controller-pilot communication by data link and no longer by voice. As for the UAT, VDL-4 is more affordable than the 1090ES for general aviation, and particularly tourism aviation.
Application
The first application is monitoring : ADS-B data is in fact much more precise than that of radars, since their accuracy is GPS. A second application of ADS-B, using reception, is the ATSAW (Airbone Traffic Situation Awareness), allowing pilots to have a precise image of the air traffic around them.
However, just like maritime AIS, only aircraft equipped with ADS-B will be on view to pilots. Transitional measures will therefore be necessary, and studies are still underway in Europe to resolve the transition from “all RADAR” to a mixed solution.
Finally, and it's not the least problem, ADS-B being unencrypted, anyone can track air traffic with a simple ADS-B receiver, which can pose security problems. In addition, a hijacked plane that knows surrounding traffic could be directed towards another plane in mid-flight. This new risk is, we doubt it, the subject of debate in the USA.
This is particularly true that applications for monitoring aircraft are now available for a few dollars for iPhone and iPad, as Plane Finder that uses an ADS-B data stream in real time to display the position, flight and identification of all aircraft equipped with ADS-B. Exactly like the data flows of Marine Traffic or SiiTech (*) for marine navigation.
Deployment
From 2009, the FAA deployed ADS-B stations (1090ES and UAT) on its territory, and plan to make the system mandatory until 2020. Europe, well covered by radar systems, is still in the experimental phase. China, Australia and other countries began deploying the system several years ago. France will equip the area of Ile de la Réunion and then extend this system to all areas difficult and expensive to equip with radar (Polynesian archipelagos, Guyana, aso.)
To conclude with a little humor, the question of seaplanes came to me. commonly used in Africa, in Canada and the USA, will they have to equip themselves with ADS-B or AIS, or both ? Ou bien verra-t-on un jour la fusion des deux systèmes sur un seul écran ? Les fabricants d’électronique ont du pain sur la planche pour quelques années ! 🙂
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(*) AIS reception on the web
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Source :
Wikipedia
http://www.aero-hesbaye.be/ADS-B.htm
http://www.ads-b.com/
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