Article

2004-01-30 Europe

Russia to construct its own global navigation system

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Posted by Steve White 2004-01-30 1:43:50 AM|| || Front Page|| [11128 views since 2007-05-07] Top

#1 capable of determining the object coordinates to within 10 meters.

I thought it was 2 meters. And I thought the only difference between the mil version is the rate at which the updates come in from the sat.

Posted by Rafael 2004-1-30 2:27:19 AM|| 2004-1-30 2:27:19 AM|| Front Page Top

#2 22 meters for the higher accuracy version, I believe. 10 meters is what European system is aiming for. Interesting info in this pdf brochure. Accuracy degradation was apperently deactivated for mass-market users in 2000, and the Europeans are worried about the economic consequences should the US government decide to switch-on accuracy degradation again.

Posted by Rafael 2004-1-30 2:49:58 AM|| 2004-1-30 2:49:58 AM|| Front Page Top

#3 Sorry for the triple posts. But I especially liked this quote from that pdf file:

As our economic dependence on GPS grows, Europe can be held to ransom on all issues related to its use of the GPS and might be obliged to pay governmental levies to the US in the future. Europe cannot accept this.

Got'em by the balls, heh heh. Why wasn't this brought up at the UNSC earlier?

Posted by Rafael 2004-1-30 3:00:32 AM|| 2004-1-30 3:00:32 AM|| Front Page Top

#4 I thought Glonass had already been in existence for a decade or more?

Posted by gromky 2004-1-30 3:38:59 AM|| 2004-1-30 3:38:59 AM|| Front Page Top

#5 LOL Gromky.... actually they do have a satnav system but I think it has a limited horizon.

Posted by Shipman 2004-1-30 8:09:49 AM|| 2004-1-30 8:09:49 AM|| Front Page Top

#6 A couple of clarifications:

1) The GPS system has two subsystems. The civilian-use system has a non-degraded accuracy of 10-15 meters, depending on your location (i.e. 'urban canyons' with high buildings can result in less accuracy). The military can turn on "selective degradation" which unpredictably degrades the accuracy to as much as 30-40 meters. It is this which has been turned off for some time now, as civilian use of GPS exploded.

2) The military has a separate subsystem that broadcasts over different frequencies. Suffice it to say that it is more accurate than the non-degraded civilian band.

3) Either band's accuracy can be improved greatly using "differential GPS". This means planting a radio source that sounds like a GPS satellite at a fixed and precisely known location on land (or theoretically, at sea). By factoring in the differential beacon's info, it's possible to filter out the degradation and much of the inaccuracies of the civilian band. Such beacons might reasonably be taken off line (forceably if necessary) to prevent their use by attackers.

4)Surveyors use a totally different approach to get centimeter accuracy. They ignore the content of the satellite measages and measure doppler effects on the signals as signals. This requires being stationary for a minute or more and is usually enhanced with a differential beacon of some kind.

5) GLONASS was indeed started, the constellation of satellites was not completed and it functions in a somewhat different way than GPS. I forget the technical approach the Soviets used in GLONASS. In GPS, the satellites send messages that are time-stamped to atomic clock accuracy. The GPS receiver notes the actual time the message was received and, based on the difference, infers the distance to that satellite. When 3 or more satellites are used this way, it is possible to estimate location by reference to an 'ephemeris table' that specifies where exactly the satellites are overhead at any time.

These estimates are made and refined continually. Apart from selective degradation, inaccuracies can occur for several reasons. First, the little computer inside the receiver, and its computing algorithms, can be underpowered or imprecise. Obviously, there is a cost/benefit tradeoff when designing receivers for various purposes. Second, location is inferred from distances and distances are inferred from timestamps. If, for instance, that message's radio signal bounced off of a building or two before reaching your receiver, the inferred distance will be incorrect - this is the 'urban canyon' problem in places like Manhattan.

Posted by rkb 2004-1-30 9:38:28 AM|| 2004-1-30 9:38:28 AM|| Front Page Top

#7 Damn, RKB. Thanks for the lesson. Yet another reason I love Rantburg.

Posted by mjh 2004-1-30 10:18:31 AM|| 2004-1-30 10:18:31 AM|| Front Page Top

#8 Why not just buy a Caddy with the Onstar system? If they lock their bottle of vodka in the car, Onsta can remotely open their doors.

Posted by Unmutual 2004-1-30 11:01:07 AM|| 2004-1-30 11:01:07 AM|| Front Page Top

#9 For the techies, here is an online table comparing the data available from GLONASS & GPS.

Also for techies, the software in GPS receivers usually includes an adaptive Kalman filter to smooth and improve location estimates over time. A glance at the GPS data shows that it offers a lot more parameters than the GLONASS system, thereby giving receiver designers more to work with. Not all receivers use all of these parameters, however ... that old cost/benefit thing comes into play.

Posted by rkb 2004-1-30 11:37:12 AM|| 2004-1-30 11:37:12 AM|| Front Page Top

#10 Study this carefully. It will all be on the Midterm...

Posted by PBMcL 2004-1-30 12:05:33 PM|| 2004-1-30 12:05:33 PM|| Front Page Top

#11 Also, RKB, newer civilian GPS receivers can receive the new Wide Area Augmentation Service (WAAS) signals. With WAAS, the receiver can get 3 meter accuracy.

Posted by Robert Crawford 2004-1-30 12:20:04 PM|| [http://www.kloognome.com] 2004-1-30 12:20:04 PM|| Front Page Top

#12 Yes. WAAS is a form of differential GPS. Receivers generally are built specially for this (at least, with special software) in order to ensure that they give the info from the differential beacon more credibility than the info from the satellite constellation.

When I was working with this stuff in the early / mid 90s, there were huge battles over civilian & commercial aircraft using GPS. Stanford did research into putting very accurate differentially-enhanced receivers on aircraft wingtips and using them to do full landings under computer control - managing pitch and yaw off of the difference between the two receivers' readings.

DOD wanted a new system of their own if the FAA and others were going to be allowed to turn off selective availability forever ... I haven't kept up with the battles over that but don't think much has advanced since then. Given our heavy use of military GPS in things like JDAMs, it will be a complex migration if it ever happens.

Back in the early 90s, all I was doing was accurately locating mass transit vehicles in order to initiate things like stop announcements, engine diagnostics etc. But even that modest goal required much better than 40 foot accuracy so some transit agencies backed the FAA's push for WAAS would blanket the country so they could use the beacons for free, too.

Gawd, it's been a while since I've even thought about those projects!

Posted by rkb 2004-1-30 12:47:22 PM|| 2004-1-30 12:47:22 PM|| Front Page Top

#13 And I still can't get a decent picture on my rabbit-ear TV.

Posted by Lucky 2004-1-30 12:57:36 PM|| 2004-1-30 12:57:36 PM|| Front Page Top

#14 I hope the Russian GPS-clone is more accurate than their maps. The Soviet Union deliberately built in errors into their maps, in case they were ever stolen or captured by the enemy. If you weren't taught how to use the maps with a correction factor, you'd be off by up to several thousand meters.

Posted by Old Patriot 2004-1-30 1:31:05 PM|| [http://users.codenet.net/mweather/default.htm] 2004-1-30 1:31:05 PM|| Front Page Top

#15 I've heard the same thing OP... But they do make 'em pretty.

Posted by Shipman 2004-1-30 2:00:47 PM|| 2004-1-30 2:00:47 PM|| Front Page Top

#16 4)Surveyors use a totally different approach to get centimeter accuracy. They ignore the content of the satellite measages and measure doppler effects on the signals as signals. This requires being stationary for a minute or more and is usually enhanced with a differential beacon of some kind.

and

the software in GPS receivers usually includes an adaptive Kalman filter to smooth and improve location estimates over time.

These have been combined in a recent civilian model. It has an option for locating itself at startup to high accuracy. You set this option, then put it down and leave it there for several minutes. It'll beep when it's located itself to an accuracy less than 10 centimeters. This gives you a high quality starting point.

The process can be repeated to help reset the receiver any time you like, thereby improving accuracy to an amazing degree.

Ed.

Posted by Ed Becerra 2004-1-30 2:54:02 PM|| 2004-1-30 2:54:02 PM|| Front Page Top

#17 Does this mean I can expand my BenchMark collection? I'm in the market for a 432 footer.

Posted by Shipman 2004-1-30 3:48:27 PM|| 2004-1-30 3:48:27 PM|| Front Page Top

#18 Nobody will buy Russian made GPS guided munitions right now because the US could simply turn off the GPS system and render the munitions useless. So naturally both Europe and Russia have decided to create their own GPS so that the flow of arms to questionable folks can continue.

Posted by ruprecht 2004-1-30 4:42:43 PM|| 2004-1-30 4:42:43 PM|| Front Page Top

#19 Ruprecht, now there's an angle I didn't think about, lol!

Posted by Rafael 2004-1-30 4:50:48 PM|| 2004-1-30 4:50:48 PM|| Front Page Top

#20 The problem with this is that the only one's that would be able to fix the Russians/EU's GPS after it's damaged is us. It's not exactly like they have shuttles. So we can go up and hijack they're GPS.

It's not like the Russians put locks on their satellites.

Posted by Charles 2004-1-30 7:21:39 PM|| 2004-1-30 7:21:39 PM|| Front Page Top

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