Re: Myth of GPS Employing the Nonsense of SR and GR

On Aug 10, 11:23 am, Timothy Murphy <t...@xxxxxxxxxxxxxxxxxxxxxx>
wrote:
Sam Wormley wrote:
Here we are, 100 years after General Relativity
and it continues to generate more hype and heat
than light and advances.

Potter, you seem to be pissed that a theory you can understand
contributes to a very useful application, namely global navigation
satellite systems (GNSS) that has resulted in a $30B+ industry,
creating a global infrastructure benefiting people all over the world.
Aviation, shipping, asset management, survey, mining, agriculture, time
dissemination, communications networks...

Although Potter's postings seem fairly nonsensical to me,
I wouldn't have thought GR was relevant to GPS?
SR, conceivably, even though I would have thought
the discepancies from Newtonian theory would be negligible in this area.

At GPS altitudes, the effect of gravitation is stronger than
the effect of relative velocity between satellite and ground station.
Though both are terms in the same GR calculation, the
gravitational term (+45 usec/day) is colloquially called "the
GR effect" and the velocity term (-7 usec/day) is colloquially
called "the SR effect".

But it is a GR calculation that predicts this net 38 usec/day
effect. That doesn't sound like much, but to achieve the
accuracy desired from GPS, the designers like to keep the
space clocks within a few nanoseconds of the ground
clocks. A 38 microsecond drift is thousands of time too
large to support the desired accuracy, so it's not a
"negligible discrepancy".

Ps I do not dislike GR!
I would have thought that something like it
is necessary to make sense of space-time.

- Randy

.

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