[teqc] MultiPath with L1 GPS receiver

Lou Estey lou at unavco.org
Thu Feb 3 19:21:37 MST 2005


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

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Louis H. Estey, Ph.D.              office:  [+001] 303-381-7456
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