[ntp:questions] lots of GPS modules and info at SparkFun

David J Taylor david-taylor at blueyonder.co.uk.invalid
Thu Feb 9 09:18:53 UTC 2012

> Hi David,
> I'm certainly considering that board.  It looks very attractive.  I'm 
> going to have to read over the documentation page you've put together. 
> It looks very comprehensive.
> Chris Albertson said to get a unit which had:
>      1) - a stationary mode, or possibly only a stationary mode
>      2) - self survey
>      3) - PPS
>      4) - serial output
>      5) - NTPD driver support
> Now I know the Sure board has 3) and 4).  And I presume you can do 5) 
> through the generic NMEA driver.  However, do you know if it can do 1) 
> and 2)?  Actually, does it have native PPS, or are you adding it by 
> using the LED output?
> Sincerely,
> Ron

(1) and (2) are not required for the microsecond level accuracy you are 
going to see in an NTP application, Ron.  In common with other GPS timing 
devices, the Sure board doesn't have those features, or if it does, I've 
not used them.  It's my understanding that they only become significant 
below the microsecond level.  Other uncertainties will contribute rather 
more than (1) or (2) will reduce.  (1) might help if you don't have a 
reliable view of the sky - in practice with today's sensitive receivers 
being on the top floor of a building with just the roof in the way may 
well be enough, particularly in a domestic environment.  See how well 
other GPS devices perform in your location.

Any further questions which aren't answered on my Web page, please ask.


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