[teqc] upcoming improvements to teqc's qc antenna position calculation

Geoffrey Blewitt gblewitt at unr.edu
Fri Mar 9 13:50:00 MST 2018


As Neil Ashby writes, the Sagnac effect is only that part of "r dot v" from Earth rotation.  So perhaps this is a problem of terminology.

Personally I think its easier to forget the Sagnac effect and just think of correcting the satellite position for light travel time in the inertial frame, for example, by correcting the Earth-fixed satellite velocity for Earth rotation. 

So in summary, either (1) do the light tine correction in ECI frame, or (2) do it in ECEF, but correct for Earth rotation = Sagnac effect.


- Geoff

> On Mar 9, 2018, at 12:25 PM, Lou Estey <lou at unavco.org> wrote:
> Richard, Geoff,
> Yes, the Sagnac effect, as you know, is a relativistic correction due to the Earth's rotation
> and is proportional to "r dot v" of the SV's position and velocity at the time of signal
> transmission: in the IS-GPS-200, or Section III in Neil Ashby's 2006 summary paper
> https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.aapt.org%2Fdoorway%2FTGRU%2Farticles%2FAshbyarticle.pdf&data=01%7C01%7Cgblewitt%40unr.edu%7C1981573474ea42a2d4b408d585fbf4bd%7C523b4bfc0ebd4c03b2b96f6a17fd31d8%7C1&sdata=NsCU4UnC4iSIw4IYfGAD8%2FBfse79cz2Z71oxyMfIKzA%3D&reserved=0 on relativistic effects.
> Time correction for signal propagation time (on the order of 0.1 second) during the Earth's
> rotation is, e.g., covered here: https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.navipedia.net%2Findex.php%2FSatellite_Coordinates_Computation&data=01%7C01%7Cgblewitt%40unr.edu%7C1981573474ea42a2d4b408d585fbf4bd%7C523b4bfc0ebd4c03b2b96f6a17fd31d8%7C1&sdata=1OjrqMXsMLJfkYXe0KjEH5IXFgbhOs9rAfPxkvOIS5U%3D&reserved=0
> I can send either of you two trial executables: one with the Sagnac effect off and the
> other ignoring the Earth's rotation during the signal travel time to the antenna.
> --lou
>> On 09-Mar-18 01:03 PM, Geoffrey Blewitt wrote:
>> Lou
>> I agree with Richard, accounting for Earth rotation in the ECEF frame IS the Sagnac effect.  Its is also equivalent to computing in the ECI frame (like GIPSY does).
>> Just hope you are not counting this twice.
>> Thanks,
>> - Geoff
>>> On Mar 9, 2018, at 11:52 AM, Richard Langley <lang at unb.ca> wrote:
>>> Lou:
>>> Aren't these the same thing? That is, in the Earth's rotating frame of reference (e.g. WGS 84), the Earth rotation correction IS the Sagnac effect.
>>> -- Richard
>>> -----------------------------------------------------------------------------
>>> | Richard B. Langley                            E-mail: lang at unb.ca         |
>>> | Geodetic Research Laboratory                  Web: https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fgge.unb.ca%2F&data=01%7C01%7Cgblewitt%40unr.edu%7C774951b84d5e4a6cb0a008d585f74283%7C523b4bfc0ebd4c03b2b96f6a17fd31d8%7C1&sdata=%2BTwS2iSLv490Bgaijk13IuFR3zwmVnd%2FBnM3FITsOSc%3D&reserved=0     |
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>>> -----------------------------------------------------------------------------
>>>> On Mar 9, 2018, at 2:41 PM, Lou Estey <lou at unavco.org> wrote:
>>>> - the relativistic Sagnac correction to each SV position calculation,
>>>> - accounting for the rotation of the Earth during the travel-time of signals
>>>>  from each SV to the antenna

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