[time-nuts] Motion effects on accuracy of GPS pps
ddavson at peralex.com
Tue Jun 29 08:13:28 UTC 2010
I've recently completed a GPSDO using the pps output of a uBlox Antaris
TIM4 GPS module to discipline a 10MHz OCXO. I'm now investigating the
motion effects (acceleration/uniform velocity) on the accuracy of the
time-pulse and hence on my frequency output.
I've been unable to find any detailed information on the relationship
between the accuracy of the pps output and the effects of having the
receiver in motion (i.e. in a car/boat, at velocities far below the
modules operating limit of 515m/s) - I'd appreciate some input on this
matter. Does motion cause increased jitter? Is it possible for it to
cause a phase error in the pps output for a finite duration? I suspect
that the averaging I am doing on my phase measurements will eliminate
the effects (600 samples, 1 second apart), but if the error introduced
is significant I'll most likely add monitoring of the DOP information
and disable the GPSDO when the TDOP is too high.
The product's system integration manual does indicate that is possible
to use an accuracy mask, which theoretically imposes a limit on the
accuracy of the output, however this information is quite vague -
emailing uBlox support has yet to yield a response.
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