GPS satellite navigation system doesn't use, doesn't need and doesn't prove Einstein's General Relativity.
The GPS satellites use classical (Newtonian) relativistic principles to work. These are the same relativistic principles that make sense in the everyday world, that most people equate with 'common sense'. GPS calculates positions based on geometric principles. The atomic clocks on the satellites have their rates preset in order to match experimentally observed effects. No General Relativity is used or needed.
The website dedicated by the USA government to the GPS system, www.gps.gov, has a lot of information for those who want to know how GPS works, but does not put forward anything about General Relativity (GR).
The equations used by the GPS system are based on geometry and classical relativity. They dont include compensations for GR effects. The satellite simply sends out a signal at regular intervals with some information. The receiving device does all the required calculations with the signals it receives. You can check out the basics at http://en.wikipedia.org/wiki/Global_Positioning_System
When the clocks of each satellite were set, the rate of each clock was adjusted according to previously observed effects. Experimental observations over decades, showed how speed and altitude affected the rate of ticking of atomic clocks. It had been experimentally observed that atomic clocks speed up at higher altitudes. It was also observed that the speed of the clock also affects the rate of ticking. Based on these experimental observations, the GPS engineers had to adjust the rate of the atomic clocks based on what had been observed - regardless of what any theory said. The engineers knew how the clocks would be affected in orbit because of experimental observations. Not the theory of general relativity. Supporters of Einsteins GR had to make sure their theory fits these observations. The GPS engineers didnt use GR to work out how much to change the clocks.
More detail:
www. freerepublic.com /focus/chat/1025790/posts
"In the 1990's, he [Van Flandern] worked as a special consultant to the Global Positioning System (GPS), a set of satellites whose atomic clocks allow ground observers to determine their position to within about a foot. Van Flandern reports that an intriguing controversy arose before GPS was even launched. Special Relativity gave Einsteinians reason to doubt whether it would work at all. In fact, it works fine."
"At high altitude, where the GPS clocks orbit the Earth, it is known that the clocks run roughly 46,000 nanoseconds (one-billionth of a second) a day faster than at ground level, because the gravitational field is thinner 20,000 kilometers above the Earth. The orbiting clocks also pass through that field at a rate of three kilometers per second -- their orbital speed. For that reason, they tick 7,000 nanoseconds a day slower than stationary clocks. To offset these two effects, the GPS engineers reset the clock rates, slowing them down before launch by 39,000 nanoseconds a day. They then proceed to tick in orbit at the same rate as ground clocks, and the system "works." Ground observers can indeed pin-point their position to a high degree of precision."
"in Einstein's theory the relevant speed is always speed relative to the observer, it was expected that continuously varying relativistic corrections would have to be made to clock rates. This in turn would have introduced an unworkable complexity into the GPS. But these corrections were not made. Yet "the system manages to work, even though they use no relativistic corrections after launch," Van Flandern said."
www.alternativephysics.org/book/GPSmythology.htm
"The presence of Special and General Relativity effects has no bearing on the accuracy of GPS operation. In summary, it wouldn’t matter whether clocks aboard GPS satellites ran faster or slower than Earth’s clocks or even changed their speed each day. Just so long as the satellites’ clocks remained synchronised with each other and the time-difference relative Earth’s clocks didn’t become too large, GPS receivers would continue to calculate their correct position."
The following articles make the claim that GPS requires General Relativity, but in error. They refer to the initial clock rate presets as being due to GR, when the reality is that these presets had to be done, theory or not, because of experimental observations.
www.astronomy.ohio-state.edu/~pogge/Ast162/Unit5/gps.html
This article is cited in many articles and publications that are supportive of the theory of general relativity, inclucing wikipedia references. Yet, it is just opinion. In it, Richard W. Pogge makes these 2 claims without supporting them in the text. The references cited at the end of this article dont refer to relativity at all - they link to the GPS FAQ at the FAA.
1 "However, because the satellites are constantly moving relative to observers on the Earth, effects predicted by the Special and General theories of Relativity must be taken into account to achieve the desired 20-30 nanosecond accuracy." 2 "For example, to counteract the General Relativistic effect once on orbit, they slowed down the ticking frequency of the atomic clocks before they were launched so that once they were in their proper orbit stations their clocks would appear to tick at the correct rate as compared to the reference atomic clocks at the GPS ground stations."
Wandera asks: In an article that claims GPS as a real world example for relativity, why doesnt the author back up such important claims? The firt claim isnt even explained, and isnt backed up at all. The second claim labels the effect G Relativistic, but this is another unsupported opinion.
www.aticourses. com/global_positioning_system.htm
"The corrections that must be applied include signal propagation delays caused by the ionosphere and the troposphere, the space vehicle clock error, and the user’s receiver clock error." "Other error sources and modeling errors continue to be investigated. For example, a recent modification of the Kalman filter has led to improved performance. Studies have also shown that solar radiation pressure models may need revision and there is some new evidence that the earth’s magnetic field may contribute to a small orbit period variation in the satellite clock frequencies." "RELATIVITY The precision of GPS measurements is so great that it requires the application of Albert Einstein’s special and general theories of relativity for the reduction of its measurements."
Wandera says: The claim about general relativity isnt true and the article makes no attempt to back up this claim. Its nothing but opinion.