[time-nuts] 5370B on eBay, carrier phase tracking GPS receiver

Dr Bruce Griffiths bruce.griffiths at xtra.co.nz
Sun Feb 18 21:50:09 EST 2007


Brooke Clarke wrote:
> Hi Didier:
>
> Many GPS receivers output carrier phase data but it's usually used in 
> post processing to get survey grade position accuracy.  Since the code 
> phase position accuracy is larger than a wavelength the receiver does 
> not know how many integer wavelengths to add.  But because of satellite 
> movement this can be figured out later.
>
> The exception is the "in development" carrier phase timing which as far 
> as I know can only be done using the Ashtech Z12.
> The Motorola GPS receivers have carrier phase data available, but when 
> the 8 channel models were current there was no way to use it without 
> spending a small fortune.  I think today there's a Motorola binary to 
> RINEX converter.
>
> Have Fun,
>
> Brooke Clarke
>
>   
Brooke

It is not necessary to use a dual frequency phase tracking receiver to 
significantly improve the disciplining of an OCXO over the performance 
with a timng receiver.
A single frequency phase tracking receiver is more than adequate.
The largest problem is determining the ionospheric delay.
However this can be done by exploiting the difference between the phase 
and group velocities in a dispersive medium (like the ionosphere).
Carrier phase measurements can be combined with code tracking 
measurements to derive the difference between the phase and group delays.

Commercial implementations of this technique are available from Quartzlock.
They use a single channel receiver, which switches between satellites.

Disciplining an oscillator frequency is an easier problem than deriving 
a geodetic solution, constant time offsets are of little consequence.

Bruce



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