[time-nuts] Multipath Testing

Magnus Danielson magnus at rubidium.dyndns.org
Sat Mar 7 20:13:10 UTC 2009

Brooke Clarke skrev:
> Hi:
> I would like to have a way of measuring the multipath effecting my house GPS 
> antenna both in terms of it's effect on position and on timing.  Can this be 
> done using the M12+T?

To some degree you can do this. It is a bit tricky since you need to 
recall a few things:

1) Each receiver behaves somewhat differently to multipath.

2) Multipath degradation is per sat and due to orientation on the sky.

3) The aggregate error and multipath offset depends on the set of 
satellites being chosen. Adjustments on aggregate position/time needs to 
account for sats actually tracked. Best thing is to correct for each sat 

Preferred is to measure multiple passages of sats using a stable local 
oscillator to steer the clock in the receiver. The pseudo-ranges of 
trackes sats should be extracted rather than aggregate position along 
with ephimeris data. RINEX files is a suitable format to dump. Such 
dumping is however not something which all receivers support.


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