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As you undoubtedly know, even the most upbeat enthusiasts of satellite navigation have been “worrying-in-public” about so many problems. To name just a few — a large and growing onslaught of L-band interference sources; satellite aging; GNSS interoperability growing pains — the litany goes on and on. Especially with expected air traffic growth, continued reliance on methods that are now decades old would jeopardize future operation.

I’m not the only one anxious to see the requisite sea change in robustness. Within limits (not wanting to come across like a self-appointed guru nor any kind of trouble-maker) I’ve been beating the drum. My concerns have appeared in ION Journal, InsideGNSS, GPSWorld news + articles (Feb. 2008 & Dec 2009) + TechTalk Aug. 2010 & July 2008 plus Air Traffic Control Journal (Summer 2008) and a nine-minute YouTube presentation, and published articles (some of them can be downloaded from this site).

What’s been used up to now has clearly earned its highest praise and accolades — but continuation of that success is by no means assured. Solutions offered by the methods under discussion here — crucially — are available at low cost. Partial information, largely wasted but fully usable from any channel coming from any constellation’s satellites, can provide intrinsic interoperability for producing precise streaming velocity (table at the bottom of the flyer) with rigorous integrity testing for each separate measurement. In addition, this flexibility will enable ready adaptation to changes in future conditions — another major benefit absent from today’s systems.

I don’t expect dramatic changes overnight in systems already mechanized nor in plans that have gone so far for near-term updates, To look at the longer time span (or not so long if major problems arise soon), though, modest-sized projects like yours will become especially valuable. They will expedite remedial action, mitigating future emergencies.

In order to do this, you’ll need accurate carrier phase (e.g., at 1-Hz, but with discontinuities and unresolved cycle counts entirely acceptable) from your GPS unit. Most of what you can buy won’t give that, but the capability can be had at low cost. I’m really glad to hear of your involvement in these developments. It shows your awareness of the huge opportunities awaiting those who use the info to provide needed direction. I’m glad to be communicating with you once again and I’m quite optimistic about your success in this effort,
JLF

Very cool – I want to try this. I’m think about how this would improve current HUMS systems, which typically need a serial interface into the aircraft avionics. It seems that, due to the complexity of just interfacing with existing systems, it would be better to role your own GPS system. This would be a great technique to implement. This would support FOQA, a FFA future requirement for medium/EMS helicopter (hence, a good thing to role into HUMS)

thx
Eric

A blog “Collision avoidance by deceleration” at http://jameslfarrell.com/gps-gnss/332
has a link to a 10-minute YouTube presentation. It’s for aircraft, so it would require much change for application to cars. But some of the principles would be relevant — e.g., transmitting measurements NOT coordinates would provide a giant improvement in performance.

That basic idea, “Send Measurements, not Coordinates” is the title of a 1999 Institute-of-Navigation Journal paper (v46, n3) showing, in the Introduction, eight reasons for dramatic supeiority of measurements over coordinates (e.g., cancellation of major errors; no augmentation system needed; retention of partial information when some satellite signals are missing; optimization of estimates for dynamics as well as position; insensitivity to misunderstanding of datum reference; etc.). An Air Traffic Control Journal (Summer 2008 issue) lists an even longer set of considerations. Although written for aviation, many of the principles are applicable to cars as well.

I have other blogs on the website that also overlap the topic to some extent. In addition, over 100 pages of a recent book are freely viewable. The longest chapter of that book, the ninth, concentrates entirely on tracking. I hope this information will be found useful to you.