There will still be people who remember what a VHS cassette looked like and a few who remember the epic technology war between Betamax, System2000 and VHS. More recently, the Blu-Ray disc won in a similar battle in the consumer electronics field only to face quick extinction as the world moves towards on-line entertainment distribution.
In air traffic management such an epic battle was raging a few years ago between VDL Mode 2 and VDL Mode 4. They were vying for the privilege of becoming the prime technology for air/ground digital link, one of the most important enablers of the new air traffic management system. VDL Mode 2 won in the end mainly for practical reasons and certainly not because of technical superiority.
A cursory glance at the surveillance landscape shows that yet again there are two technologies aiming to replace expensive and cumbersome radar and one might conclude that a new technology war is in the offing.
The technologies concerned are Automatic Dependent Surveillance-Broadcast (ADS-B) and Multi-lateration (MLAT). Just to recap, ADS-B is a surveillance solution where
aircraft broadcast their GPS-derived position (ADS-B out) and the messages received on the ground are used to create air situation displays for air traffic controllers. When aircraft are able to receive the same messages (ADS-B in), these enable them to do airborne separation assurance, among other things.
Multi-lateration uses the replies from SSR transponders, timing their arrival at ground receiving antennas and calculating aircraft position from those time differences. WAM is Wide Area Multilateration, in effect the MLAT technology applied for surveillance in a given area.
The potential accuracy of both technologies is phenomenal and is far better than that of conventional radar. The icing on the cake is that the cost of implementation and ownership is a fraction of those outdated monsters.
Multi-lateration does not require any additional equipment on board the aircraft and hence it represents the larger potential savings. ADS-B (in and out) does require investment from the airspace users but it also provides more extensive capabilities than MLAT does (see below).
Although for airport surface surveillance applications as yet only MLAT seems to be accurate enough, there is no technical reason why ADS-B should not catch up in the near future.
So, a new technology war? Luckily, no!
It would seem that we are heading towards a future where both WAM and ADS-B will have its place and where WAM will be more than just a stepping stone towards ADS-B. One of the main drivers behind WAM is the fact that it does not require any new equipment on board aircraft. Hence it is much easier to make a business case for WAM implementation since the savings from replacing radars are more directly applicable to the new system without the need to argue about on-board costs, a challenge at the best of times.
ADS-B is of course progressing in the US, Canada and Australia where the prevalence of remote areas does legitimize this slightly more expensive technology.
In Europe, WAM systems are proliferating on airports as well as over various water bodies, primarily to watch over helicopter operations. But its application for other types of traffic is only a matter of time, there is little doubt about that.
It is a fundamental truth that any surveillance system must have full coverage if it is to be usable safely and effectively. This translates to nearly 100 % equipage with ADS-B if that technology is considered to be the aim in the longer term. Clearly, achieving this is a tall order even if there will be a business case everybody agrees on. And we are not there yet…
Multi-lateration on the other hand is available now, it is being implemented and will start delivering benefits as soon as conventional radars can be hauled to the scrap yard. It can certainly offer a cheaper alternative to radar as well as a path towards ADS-B.
It would seem indeed that ADS-B and WAM are complementary in both timing and capabilities and will not be the subject of an expensive and counter productive technology war.
Some experts believe that we will forever be stuck in this transition towards ADS-B since WAM will provide the desired lower cost surveillance solution and the need for ADS-B in/out will not be substantial enough to ensure its universal adoption particularly in view of its higher costs for the airspace users.
One can only hope that the specter of a technology war will not be replaced by a slowing down of ADS-B implementation! WAM can do a lot of things except to act as the tool for airborne surveillance. Without airborne surveillance, no separation assurance from the air and this would equate to the killing of an important feature of SESAR in the overall package of new separation methods.
Cost and availability are important in respect of all technologies but they remain enablers for other things and not the aims themselves. The SESAR Concept of Operations does describe new methods of working which require certain enablers and for the moment, only ADS-B can provide the support needed.
It is a good thing that WAM and ADS-B will not be waging a war but they should not cozy up too much either, divvying up the territory. We will need full ADS-B in/out if the SESAR CONOPS is to become reality.