GPS satelite Clock Error Explanation

[jayoakam]

Hello,

I am new to these forums. Does the EU have an explanation of the GPS satelite clock Error? GPS satelites clocks are adjusted before launch to allow for the relativistic effects of gravity. I did not read in Dr. Scott's rebuttal of TB any explanation of this adjustment which TB raised. I did a search of the forums on "GPS+error" and found no references. The gravity and time error have been shown by experiment (aircraft and satelite) to show relativistic effects. What is the EU theory concerning this?

John Yoakam
(EE + Plasma Science + EU) Advocate

[nick c]

Hey jayoakam,
I am not a physicist and will leave responses to this issue to those more qualified, however, I did find this interesting article:
[url2=http://www.physicsmyths.org.uk/gps.htm]GPS and Relativity[/url2]

Now the quoted relativistic correction of 38 microseconds/day corresponds to ε=4.4.10^-10. As the satellites are at a distance of around 20000 km (=2.10^9 cm), the positional error due to relativity should actually only be 4.4.10^-10 . 2.10^9 cm = 0.8 cm! This is even much less than the presently claimed accuracy of the GPS of a few meters, so the Relativity effect should actually not be relevant at all!
highlights added

nick c

[jayoakam]

Thanks for the post.

I understand the corrections are small - what I want to understand is how the EU theory explains the need for a time correction as opposed to relativity's explanation. Specifically, Dr. Scott did not address the TB statement that the GPS time corrections are confirmation of relativity. I have read Dr. Scott's book "The Electric Sky" (I am a big fan of Dr. Scott) but I can't find a EU explanation of the relativistic effects that have been measured.

Is there a way to ask Dr. Scott for his analysis?

Thank you all in advance.

John Yoakam

[StevenO]

Now the quoted relativistic correction of 38 microseconds/day corresponds to ε=4.4.10^-10. As the satellites are at a distance of around 20000 km (=2.10^9 cm), the positional error due to relativity should actually only be 4.4.10^-10 . 2.10^9 cm = 0.8 cm! This is even much less than the presently claimed accuracy of the GPS of a few meters, so the Relativity effect should actually not be relevant at all!
highlights added

nick c

Hi Nick,

Your assumption is not correct. Since the propagation time of the signals is measured, the 38 μs/day should be multiplied with the speed of light to calculate the error:

Taken over a full day, the net compensation needed has a magnitude of 45(GR) – 7(SR) = 38 μs. This
corresponds, by multiplying with c, with a distance of about 11.4 km a day. So, if left uncompensated
for, within 1 minute the deviation would already be substantial: almost 10 m.

[nick c]

Hi Nick,
Your assumption is not correct. Since the propagation time of the signals is measured, the 38 μs/day should be multiplied with the speed of light to calculate the error:

Hi StevenO,
Well it is not my assumption. I was merely connecting to a website:
http://www.physicsmyths.org.uk/gps.htm
which I found interesting and related to the original post. I relayed your post to the author, Dr. Thomas Smid, and asked him to clarify the material on his website, this was his response in its' entirety:

Dear Nicholas,

Thank you for your email.

Apparently StevenO has missed the point I made on my page:

The 38 microseconds/day is the drift between a satellite clock and a
ground clock. However, in practice ground clocks are not being used at
all to determine the position. It is determined by measuring the
difference of time signals from different satellites (if you have an
n-dimensional problem, one needs the time signals from n+1 satellites;
in my example n=1, so 2 satellites are sufficient there; in 3D-reality
(n=3) you need 4 satellites (see
http://en.wikipedia.org/w/index.php?tit ... id=8970438
(Technical Description)).

Everything that is required for the position determination (like the
satellite positions) is encoded in the satellite signal, and all that
the receiver does is to calculate the position from these data. So since
a receiver clock is in principle not required at all, it is therefore
irrelevant in practice for GPS, whether the ground clock accumulates an
error relatively to the satellite clocks or not.

So just to avoid any misunderstanding: I am not saying that my example
shows that a ground clock does not accumulate an error with regard to
the satellite clocks (whether or not this is the case is a different
matter I am not addressing here). I am only saying that the way the GPS
works in everyday practice, an accumulation of the alleged magnitude
(whether caused by Relativity or whatever) would be irrelevant for a
position determination. So the argument often used by Relativists that
civilization would effectively break down if Relativity is not taken
into account for GPS positioning is very much incorrect and flawed.

Best regards,
Thomas

P.S: You are welcome to post my reply in the forum if you like

Very informative, the GPS/relativity issue is interesting and more complicated than sometimes portrayed. It seems that Dr Smid, stands by his calculation (in the above linked website) of a positional error of 0.8 centimeters which is well within the accuracy limits for GPS, thus claims of verification of relativity by GPS would seem to be premature.

jayoakam:
I am searching for some EU references to the GPS/relativity issue. I'll take your word that it is not mentioned in Scott's The Electric Sky but can't check right now, as I have loaned out my copy to a friend.
I have not found any references so far, though I do remember reading something (possibly by Thornhill?) on the subject.
More later,

nick c

[StevenO]

That is very interesting Nick. That'll teach the relativists to be a little more modest next time we're having a discussion about that.

[Solar]

Item 1: From D. E. Scott Rebuts T. Bridgman

THE (NON)USEFUL PRODUCTS OF ASTROPHYSICS Also on his page 4, TB claims that the Global Positioning System requires general relativity for precise computation of transmission delay times of the GPS signals in the gravitational field of Earth. This, he claims, is a useful contribution of astrophysics. However, as with so many of the pronouncements of the astrophysics power structure, there is an alternative explanation. H.F. Fliegel and R. S. DiEsposti of the GPS Joint Program Office of the Aerospace Corporation conclude1 ―Except for the leading γ [gamma] factor [in their final equation], it is the same formula derived in classical physics for the signal travel time from the GPS satellite to the ground station. As we have shown, introducing the γ factor makes a change of only 2 or 3 millimeters to the classical result. In short there are no ‗missing relativity terms.‘ They cancel out.” General Relativity Theory is not needed.

The paper cited above by H.F. Fliegel and R. S. DiEsposti is here:
GPS and Relativity: An Engineering Overview

Item 2: From Tom Bethell at Meta Research

The simplest way to understand all this "without going crazy," Van Flandern says, is to discard Einsteinian relativity and to assume that "there is a light-carrying medium." When a clock moves through this medium "it takes longer for each electron in the atomic clock to complete its orbit." Therefore it makes fewer "ticks" in a given time than a stationary clock. Moving clocks slow down, in short, because they are "ploughing through this medium and working more slowly." It's not time that slows down. It's the clocks.
(…)
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) theory, however, it was expected that because the orbiting clocks all move rapidly and with varying speeds relative to any ground observer (who may be anywhere on the Earth's surface), and since 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. "They have basically blown off Einstein." – Rethinking Relativity by Tom Bethell

[saturnine]

It's not time that slows down. It's the clocks.

People really don't understand this? Rhetorical question folks.

[jayoakam]

Solar - thank you for the useful information - I have a better handle on it now and I am glad my GPS doesn't need any special relativity.