[teqc] MultiPath with L1 GPS receiver

James Johnson jjohnson at ucar.edu
Thu Feb 3 19:35:38 MST 2005


Ok, that's good to know.  So all Hannan should have to do is compute 
RMS values of these output files.

-Jim
On Feb 3, 2005, at 7:21 PM, Lou Estey wrote:

> James Johnson wrote:
>
>> [...]  In principle, you can do this with single frequency data over 
>> a short period of time, but after some time the L1 phase and C/A 
>> measurements will diverge due to the ionosphere (phase advance on L1 
>> and group delay on C/A).  What you want to look at is a running 
>> average of C/A - L1*lambda where C/A is the pseudo range measurement, 
>> L1 is the phase measurement in cycles, and lambda is the wavelength 
>> of L1.  If you use a running average of a 10 min, you should be able 
>> to see the multipath signal, an you could look at the RMS of this 
>> value (with steps removed caused by possible cycle slips).  
>> Unfortunately teqc does not do this.
>
> Actually, Jim, if you remember: we started down this path some years
> ago when we were researching L1-only receivers for the L1 project and
> teqc got part way there.  You can still activate the +pl option during 
> qc
> to generate the .pl1 plot file (C/A - L1*lambda) -- but we never 
> followed
> through with the running average, etc.  At the time (and it's still
> true!) the most important qc aspect was whether we were getting 
> complete
> data epochs or not -- what percentage of epochs was lost (due to 
> transmission
> or data collection problems).
>
> cheers,
> --lou
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> Louis H. Estey, Ph.D.              office:  [+001] 303-381-7456
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>
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>                                                -- Leon Lederman
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