Re: Evidences for the ether

The Ghost In The Machine wrote:
In sci.physics.relativity, Paul B. Andersen
<paul.b.andersen@xxxxxxxxxxxxxxxx>
wrote
on Mon, 04 Sep 2006 22:53:34 +0200
<edi3of$8j9$1@xxxxxxxxxxxxxxxx>:
The Ghost In The Machine wrote:
In sci.physics.relativity, Paul B. Andersen
<paul.b.andersen@xxxxxxxxxxxxxxxx>
wrote
on Thu, 31 Aug 2006 15:33:19 +0200
<ed6of0$qjj$1@xxxxxxxxxxxxxxxx>:
Sorcerer wrote:
"Paul B. Andersen" <paul.b.andersen@xxxxxxxxxxxxxxxx> wrote in message news:ed47qc$mts$1@xxxxxxxxxxxxxxxxxxx
[snip]

-------------------------------------------------------------
The clock in each satellite is synced to GPS-time once a day.
--------------------------------------------------------------
Erm...pedant point. Satellite clocks are not adjusted at all.
Instead, a delta is published once a day, which the satellite
publishes but otherwise ignores to the handheld ground-based units.

At least, such is my understanding.
Right.
But I have to simplify when discussing with idiots like Androcles. :-)
You might say that the time reported by the satellite
(which is the clock time together with the clock offset),
is corrected once a day.

Paul

True. :-) In any event, it simplifies the design;
all clocks can simply freerun, as opposed to requiring
some sort of "frequency steering logic".

However, were they to freerun at the wrong rate, then just
before the synchronization (if one takes a measurement
at 23:59 and the synch is done at 00:00 Zulu, say), one
gets a measurement error from each clock of about
3.8 * 10^-5 * 3 * 10^8 = 11.4 km. Since the spaceclocks
are running fast in this scenario the measurement point
would likely be suspended somewhere in midair, assuming
a solution to the question "Where Am I?" is even possible.

Since the error is usually touted as being 100m at most
for the civilians (and 10m for the military), this gets
slightly ridiculous quickly, especially since GPS units
(with maps) are for sale at many outlets.

The CA precision of 100 metres was with the selective
availability on (intentional degrading of the precision).
This has been switched off since May 2000, so now
the precision is nominally 30 metres, actually better
than 10 metres.

http://www.ngs.noaa.gov/FGCS/info/sans_SA/compare/ERLA.htm

Paul
.

Relevant Pages

  • Re: The Speed of Gravity =?windows-1252?Q?=96_What_the_Exp?= =?windows-1252?Q?eriments_Say?=
    ... continually changing synchronization corrections for each clock exist such that the predictions of SR are fulfilled for any local co-moving frame. ... To avoid the embarrassment of that complexity, GPS analysis is now done exclusively in the Earth-centered inertial frame. ... And the pre-launch adjustment of clock rates to compensate for relativistic effects then hides the fact that all orbiting satellite clocks would be seen to tick slower than ground clocks if not rate-compensated for their orbital motion, and that no reciprocity would exist when satellites view ground clocks. ... Now, if one can provide a way for a ground receiver to synchronize its clock with the satellite clock, a simple measurement of the time delay in the signal received from a satellite in view of the Earthbound user, should result in a precise range to that satellite. ...
    (sci.physics)
  • Re: The physics of music.
    ... changing synchronization corrections for each clock exist such that the ... that the GPS continues to operate with great accuracy has in fact ... relativity in the global positioning system, ... The design life of each satellite is 7.5 years.) ...
    (sci.physics)
  • NGA GPS Ephemeris/Station/Antenna Offset Documentation -- Effective date August 15, 2006
    ... NGA GPS Ephemeris/Station/Antenna Offset Documentation ... GPS PRECISE EPHEMERIDES, SATELLITE CLOCK PARAMETERS ... National Geospatial-Intelligence Agency and Air Force monitor station data ...
    (sci.geo.satellite-nav)
  • NGA GPS Ephemeris/Station/Antenna Offset Documentation -- Document last modified Monday, 02&
    ... NGA GPS Ephemeris/Station/Antenna Offset Documentation ... GPS PRECISE EPHEMERIDES, SATELLITE CLOCK PARAMETERS ... National Geospatial-Intelligence Agency and Air Force monitor station data ...
    (sci.geo.satellite-nav)
  • NGA GPS Ephemeris/Station/Antenna Offset Documentation
    ... NGA GPS Ephemeris/Station/Antenna Offset Documentation ... GPS PRECISE EPHEMERIDES, SATELLITE CLOCK PARAMETERS ... National Geospatial-Intelligence Agency and Air Force monitor station data ...
    (sci.geo.satellite-nav)
Quantcast