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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"
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).
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.