Within the next year, production satellites for the Japanese QZSS system, the Chinese Compass, and the European Galileo constellation will all enter service. That's not really news. The timetable was already on the slate in 2000, and for all the pratfalls and pitfalls along the way, system providers have largely stuck to their guns.
So, the evidence seems to be that it takes about a decade for the GNSS to evolve. That begs an interesting question: what will the GNSS look like in 2020?
Obviously, there will be a lot of satellites in orbit - the best guess is about 120 to 130, organised into six constellations. That means that over most of the globe, most of the time, there will be ten or more within 30 degrees of the zenith.
There will be more over the Asia Pacific than elsewhere because Indian, Chinese and Japanese systems are likely to be biased towards increased coverage close to home.
So much is given. The question is, what will we be able to do with them?
And its an interesting question, because the future of a technology that could potentially change the world is being debated, largely out of the public eye, in small arcane meetings in out of the way places around the globe.
There is one potential future. Users could have a choice. You could go out and buy a GPS receiver, or a Galileo receiver, or a Compass receiver. Because the capability of each constellation is more or less the same, the user experience will be much what it is now.
In every jurisdiction, there are powerful forces, primarily in the military and security, working to ensure that that is precisely the future we have to look forward to.
But equally, there are other forces in every jurisdiction working towards a different future. That is one where receivers can access the most convenient signals from whatever satellites happen to be available, irrespective of who supplies the satellites.
There can be little doubt that, within the various user communities, and within the operator organisations, the second future is the preferred one.
Genuine interoperability of GNSS would empower a host of new applications, especially in the fields of machine guidance and automation. Currently, these fields are held back because GPS is not absolutely reliable. But with the built-in redundancy that will soon be available, the field will explode.
Most of the operators, and some significant users, met in a workshop yesterday (30 November) ahead of IGNSS2009, the annual conference of the International Global Navigation Satellite Systems society, at Surfers Paradise on the Queensland Gold Coast in Australia. IGNSS09 starts today and will continue all week.
The take-home message from the conference is that, with the possible exception of the Japanese QZSS system, which mirrors GPS, all the systems are prisoners of their own engineering history.
There is huge design convergence. Given a blank piece of paper, there are only a few options for designing a GNSS. But there are subtle differences: in frequency; in signal coding methods; in geodetic reference systems; in timing, which mean that a receiver for one system will not work with satellites from another.
This has to be taken as a given. But it is also true that because the systems are so similar, it will be technically possible to design receivers that are capable of receiving signals from all GNSS, after the same manner as current generation GPS+Glonass receivers.
Obtaining the signal is not the nub of the problem. The real problem seems to be about enough information about the underlying infrastructure to make it possible to use the signals to obtain a solution.
Can one reference frame be reduced to another? Can time signals be compared? Can we obtain data on the satellite position and performance, fast enough, to make a difference?
Of course, the answer to all these question is yes, given both good will on the part of the operators, and appropriate international mechanisms to make it happen.
There is good news on both counts. On the strength of presentations at the workshop, there is tremendous commitment to the ideal of interoperability.
Speakers from the Chinese, Japanese and Russian organisations spoke about the need for international co-operation
In fact, it seems that there will be real competition amount system providers this decade to supply the signal of choice for manufacturers. The GPS has had it for a decade, but there is no guarantee that this will continue.
International data sharing mechanism are also starting to appear. Just two: the International Association of Geodesy, and in particular, its International GNSS Service, and the United Nation's International Committee on GNSS are positioning themselves to be one of the main sources of GNSS information for the operators.
There is still, however, much talking to be done.
Source: www.asmmag.com
