[time-nuts] Advantages of GNSS ???

[Leo Bodnar]

Bob, what are you calling "time correction"?

You are now quoting F9T which is not the product original statement related to (F9P.)

If you refer to internal Ublox adjustment of instantaneous timepulse train then it is performed at navigation rate - up to 20Hz on F9P.
F9P's rate of TP can be set from 0.25Hz to 10MHz according to the datasheet but in reality is usually wider.

TP edge quantisation is a separate issue to TP base rate adjustment and it is done at TP rate.

Leo


> Subject: Re: [time-nuts] Advantages of GNSS ???
> They go absolutely crazy updating nav?.. but they only come up with the timing correction once a second.
> 
> From the latest version of the F9T Manual UBX-19005590 - R02  on page 43: 
> The recommended configuration when using the UBX-TIM-TP message is to set both the measurement rate (CFG-RATE-MEAS) and the time pulse frequency (CFG-TP-*) to 1Hz.
> 
> Since the rate of UBX-TIM-TP is bound to 1 Hz, more than one UBX-TIM-TP message can appear between two pulses if the time pulse frequency is set lower than 1 Hz. In this case all UBX-TIM-TP messages in between a time pulse T1 and T2 belong to T2 and the last UBX- TIM-TP before T2 reports the most accurate quantization error. In general, if the time pulse rate is not configured to 1 Hz, there will not be a single UBX-TIM-TP message for each time pulse. 
> 
> Sorry if the quote comes through a bit garbled. Sometimes this cut and paste stuff does not quite do the trick. 
> Indeed it?s not 100% clear what they are doing from the docs. They say this and that here and there. The 
> bottom line is still that you can only trust the sawtooth offset data to be correct at the one second point. 
> 
> Bob