Slashdot Mirror
Russian GPS Alternative Near Completion
Russia has successfully launched another round of GLONASS satellites bringing the grand total to 18 of the navigational units online. "The GPS competitor -- first begun in the Soviet era and only recently revived after years of post-collapse neglect -- is now theoretically capable of providing coverage to the entire Russian territory, with First Deputy Prime Minister Sergei Ivanov claiming that the first compatible consumer devices will be available in the middle of next year. By 2010 Russia plans to open the system up to outside nations as well, contributing to an eventual three- or even four-system global market"
Comment removed based on user account deletion
Ok, GLONASS is not very accurate because it is far from completion - you need ground based infrastructure as well as decent satellites. This system will be good enough for Russian military as they are not too bothered about 10m spread for their multi-megaton nukes, but if you drive a car with this thing then such a low accuracy will matter a lot.
Also GPS is pretty well damn established in terms of electronics and its price - there is no way GLONASS will take any significant market share anywhere in the world apart from Russia where, as it often happens there, legislation will be used to ensure it is GLONASS on sale rather than GPS. But given level of corruption there even this won't work well.
So move along, nothing to see here, and definately not something worth reporting.
They say it can theoretically cover all of Russia because only 13 of the 18 are operational. Here's an interesting quote from the article: "The main point is to avoid the 1997 situation, when 24 sputniks were on the orbit, but only the military were making use of the system. However, it is now feared that a similar situation is apt to re-occur, since there are some problems with the development of navigation equipment for the consumers at large, although the constructor-general is trying to cope with them"
Here's one from the International Herald Tribune.
/.
Somebody please stomp out myminicity. It's seriously polluting
-a.e.mossberg
This is good news for land surveyors everywhere. Most all surveyors have switched over to GPS based equipment in the last 10 years. I have been out in the field with GPS equipment, and watched my accuracy go to hell because there were not enough satilites above the horizon. Being able to pull signals from both systems means less downtime for land surveyors, and better field accuracy.
Engaget does not have one fact correct. Topcon has been offering surveying grade GPS units that can pull signals from both the US based system, and the GLONASS system for at least 3 years.
http://www.topconpositioning.com/uploads/tx_tttopconproducts/HiPerPro_Broch_REVB.pdf
BTW, if you are wondering how land surveyors get the accuracy down to 1cm for gps, it involves using two GPS recievers and a process called RTK. In RTK one reciever (the base) is placed over a known point, and equipped with a radio transmitter. This station transmitts a correction for the GPS signal to the other reciever (the rover). The results are very accurate, and our firm has pretty much stopped using conventional total station, except where vertical accuracy is an issue (gps is only good to 10cm in vertical accuracy).
GPS satellites are not in geostationary orbit. They are in non-equatorial medium earth orbit (roughly 12 hour period).
Firstly, with regular GPS you already have more than one clock - one on your receiver, and one on each of the satellites. You can directly solve for the receiver clock bias by taking measurements to an extra satellite, hence the need to track 4 satellites for a three-dimensional position fix because of the four unknowns ( X, Y, Z, and time.)
Secondly, while GPS and GLONASS use different terrestrial reference frames, there exists a well defined transform between the WGS-84 used by GPS and the PZ-90 used in GLONASS.
Finally, in a combined GPS/GLONASS receiver it is not optimal to calculate a separate position solution for each constellation. If you track a few more satellites, you can solve directly for the clock offset between the two navigation systems and treat the range measurements as if they were all from one giant 60 satellite constellation. This actually gives you much better satellite geometry, and is often more accurate than any single navigation system on its own.
There is much research being done on the effects of combined constellations with GPS,GLONASS, Galileo and the Chinese Compass system.
US turned off the Selective Availability random errors permanently in 2000, after having done so provisionally in the 1990s. Now the FAA and everyone else relies on the full accuracy, so even though the US could turn SA back on at any time, they have a strong domestic disincentive to do so. Now the military is interested in local jamming of GPS rather than introducing errors globally.
If you're still having problems with your GPS receiver, maybe it's time to get a new one..
SA caused that, but also, you'll get that with only 3 satellites over the horizon. It takes 3 satellites to determine your position, and 4 satellites to do altitude.
yeah, what ^^ he ^^ said.
The USA is rolling out their next gen GPS, - M-Code. It gives the US the ability to control accuracy on a 'per nation' basis. (unlike the old way under C/A code where inserted inaccuracy it was regional), or the current P-code (where i believe it is all or nothing - its just whether you have the codes or not.)
These days its just* a matter of adding another receiver card. As long as your system can combine the multiple nav sources (say through Kalman filtering) the more the better. - losing one source doesn't affect you too much.
* in this game 'just' costs about $50K per unit.
You might want to read the above post for how GPS works. You don't get your position from the satilites, you just get a time encoded signal. The reciever then uses the signal from at least 3 satilites to triangulate your position. If your reciever can recieve and interperate the signal fromt the GLOSNOS satilites, there is no reason why it can't use the results to augment the results you pulled calculated from the US GPS system.
You can already do this with the US based GPS system using OPUS. Forgive my bad html, but here is the link:
http://www.ngs.noaa.gov/OPUS/
You have to set up your reciever to log satilite observations over at least 2 hours, and take a reading at least every 5 minutes. Opus uses precises satilite orbital information to post process point information. The accuracy of your results depend upon how long you run your observations, and how many observations you log. I typicall run mine over 4 hours, and get an accuracy of around 4mm horizontal. Opus is a great tool when you need to tie your land survey to WGS84 coordinates, or State plane coordinates.
GPS costs for each receiver, no different than GLONASS and Galileo. The difference is Galileo offers something like 4 different services. One of them is free service which is about the same accuracy as GPS today. The paid-for services include higher accuracy (1m IIRC) and more secure channels (or something along those lines). Secondly, the main reason Galileo is being developed, IMO, is due to the fact that the American GPS has selective availability (note: this was disabled but can, supposedly, be re-enabled) and we don't want to be left in the dark if the USA goes to war with yet another country and decides to deny access to anyone but the military.
Hmmm, that's odd. I would expect to see this behavior if the GPS was trying to resolve the integeter ambiguity of the phase measurement. Survey-quality receivers do this by using both GPS frequencies in combination with corrections from a reference GPS receiver at a previously surveyed position. Any GPS can trivially determine the fraction of the phase cycle between it and the satellite but must determine the number of cycles via statistical methods using good quality measurements and initial guesses. If this number is estimated correctly, the distance between the satellite and receiver is known to within a couple of centimeters instantaneously.
These integer ambiguities are solved for at least 4 satellites simultaneously. There are always several combination of cycle counts that will result in a good position. However, these candidates may be several meters apart. If the initial guess is wrong, it may be several minutes before a new candidate is chosen and then the switch is instantaneous (hence the jump you observed).
I didn't think a consumer single-frequency receiver could do this, even with WAAS. I would expect a single-frequency receiver to simply drift around the true position without any sudden jumps (assuming there are at least 5 satellites visible at any given point in time and there aren't any strong reflectors nearby--such as a tall building). I know consumer units take phase measurements, but all of the ones I've seen have had rather poor measurement quality due mainly to the cheap antennas they use (survey quality GPS antennas are at least 8 inches in diameter and cost hundreds, even thousands of dollars if they use a choke ring to mitigate multipath).
Not sure which system you mean in your question, but here's my take:
C/A : By altering timings (jitter) on a few satellites, say when they are on the opposite side of planet from the USA, then the regions which use those satellites will have degraded GPS. (GPS being based on precision timing / radio ranging etc. Also important to note that most GPS receivers tend to ignore the strongest Satellites (the ones overhead) so it's the satellites nearer the horizon that provide the most accuracy - so some boffin had to work out a nice algorithm where a lat/long could be entered and an area within a few thousand miles would have degraded GPS. Problem was that airlines who fly world wide were affected by this, thus good 'ol Bill Clinton got the S/A turned off.
M-code: essentially uses public/private key encryption with every nation issued a different key for essentially different virtual circuit. The US can deny service or degrade any one feed selectively. - or more likely offer 'tiered' services where those most friendly nations (UK,AUS) can have accuracy for weapon delivery, and those other 'friendly nations' (don't forget Poland), have 'meh - slightly better than C/A but not good enough for weapon delivery).
It also depends what body of water you are on. Typically only the oceans will = ~0, Lakes, rivers, ponds, etc all have their own 'level'. For example even Lake Superior is nominally 602 ft above sea level and GPS would report you at 602 ft, relative to its zero datum the ocean's sea level.
The answer is not really what you think here. GPS signals have a series of different transmitters. On each satellite, there are four for the military, two for civilian use, and two that work satellite to satellite. The sat to sat transmission help create the position that is transmitted to the ground radios. Adding a new position awareness for accuracy wouldn't be hard. .04 of a foot.
About the article, I'm glad to have GLONASS come out on consumer devices. I use a GPS/GLONASS hybrid receiver for land survey and construction lay out. We usually get about 12 GPS and 3 GLONASS on any given site, and those few extra raise our accuracy from 0.1 of a foot to
TANSTAAFL
You don't necessarily need (and probably shouldn't) rely purely on GPS for weapon delivery. Even the US hardly does it (they rather use laser tagging for 'small' devices and for large devices it hardly matters but they use separate GPS channels and other navigational sources including aircraft-based guidance and the good-ol' compass) since GPS is easily jammed by a bigger version of this: http://www.phrack.org/archives/60/p60-0x0d.txt (and yes, I have all the Phrack articles, Anarchist Cookbook and Steal This Book on my keyring USB, eat that security in the airport) and is more difficult to acquire an accurate signal when you're flying long distances at high speed. The "GPS for terrorists" scare is just another scam being run by our government to make us scared of a better version of GPS technology.
Custom electronics and digital signage for your business: www.evcircuits.com