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A GPS fudge?

 
Waterbug
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User ID: 34388912
United States
02/21/2013 11:57 AM
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A GPS fudge?
Smoking gun..?

So I'm cruising around looking for information concerning the Mercury orbit anomaly.. and find this..

Pretty interesting.




General Relativity Experiments
[link to www.alternativephysics.org]


[snip]


A GPS fudge?

What does this mean? Why is it that when calculating the GR dilation on Earth we take into account centripetal force, basing calculations only on ‘net gravity’, while on GPS satellites we ignore centripetal force? Put another way, why doesn’t the Equivalence Principle apply to GPS?

According to the U.S. Naval Research Laboratory, experiments done during the initial testing of GPS satellites in 1977 showed that unadjusted satellites overall ran faster than Earth-based atomic clocks by 442.5 parts in 1012 [5]. This equates to an inaccuracy of 38230ns per day [6] – a close fit to the SR+GR calculations shown above.

However these calculations are inconsistent with the Equivalence Principle as used in comparisons between pole & equator clocks. If the same logic was applied to both sets of clocks, the net dilation for GPS satellites would be 59960-7200 = 52760ns : 37% higher than the stated value of 38600ns. Why the difference?

Is it possible that ... GPS satellites experience NO dilation at all ?

Keep in mind that prior to the invention of satellites there was no easy way to test the SR and GR postulates properly. Up to this point the evidence was shaky, the errors large, and hence much of GR and SR was just assumed to be correct. What would happen then, when GPS was being developed, if the engineers discovered that in fact no dilation occurred?

Information like that would be pretty embarrassing, especially to the mainstream scientific community who had been preaching relativity for the past 70 years. What to do? Admit they’re wrong? Not likely! The simplest solution would be to calculate the expected amount of dilation and then claim to have built that into the satellites.

Problem solved! The theory of relativity is not only preserved, it’s also exalted to a stage where the average Joe with a GPS receiver can vouch for relativity on a daily basis. After all, who would even suspect that atomic clocks aboard satellites might actually be running at the same rate as clocks everywhere else?
Anonymous Coward
User ID: 34874784
United Kingdom
02/21/2013 12:05 PM
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Re: A GPS fudge?
GPS satellite clock are per-adjusted to take account of relativity.

If you had half a brain you would have realized that.


[link to www.google.co.uk]

hf
Waterbug  (OP)

User ID: 34388912
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02/21/2013 12:28 PM
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Re: A GPS fudge?
Thanks, but you need help with comprehension.
Anonymous Coward
User ID: 554016
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02/21/2013 12:45 PM
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Re: A GPS fudge?
Time dilation has been proven in other ways than GPS.

The decay of particles in particle accellerators for example.
Waterbug  (OP)

User ID: 34388912
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02/21/2013 12:51 PM
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Re: A GPS fudge?
Hmm..




[link to physics.stackexchange.com]

[snip]

Found the answer after drawing a blank with several experts. Two US professors of high GPS pedigree, independently explained that the '10km/day' claim presupposes that between 1 and 3 of the satellites used for a 4 satellite fix do not incorporate the 38us/day clock rate ('factory') offset. They also remarked that the GPS is often used as a time source where observed time shifts are clearly important.

I and others have been vexed by several scientific authorities publicly repeating the 10km/day position error claim without any mention of that presupposition. The question is resolved but the presupposition seems strange because relativity shifts all the observed satellite clock rates approximately equally. That presupposition seems only to allow GPS position finding to be shown to be about as susceptible to transmitter clock differences as radio-location systems such as Loran, where relativity is not a consideration.





GLP