[time-nuts] Best GPS timing

bg at lysator.liu.se bg at lysator.liu.se
Tue Feb 17 23:50:37 UTC 2009


> Hi there,
>
> I did see that in the recent GPS World receiver survey, but Javad for
> example only claims 3ns rms accuracy...
>

Where do Javad claim 3ns accuracy?

+++++
[ZA], [ZB] PPS Offset
struct PPSOffset {5} {
   f4 offs; // PPS offset in nanoseconds
   u1 cs;   // Checksum
};
Due to a hardware limitation, PPS signals are discrete with a resolution
of 25 ns. JAVAD GNSS receiver allows you to compensate for this
discreteness error by means of utilizing this message. It contains the
offset between the scheduled PPS time and the actual pulse edge's arrival
time.
++++++++

They do claim 10cm pseudo-range accuracy and 1 mm carrier phase accuracy.
Why would not the "PPS Offset" message above be an accurate "sawtooth"
measurement down to the PVT solution accuracy? Where the accuracy might be
several meters in stand alone mode going down to cm level with post
processing.

--

   Björn




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