[time-nuts] "GPS once a day issues" ?

mike cook michael.cook at sfr.fr
Mon Oct 20 05:03:48 EDT 2014


The constellation may repeat at 12hr intervals , but at any static position you will only see one per day , no? , the other being 180 degrees way.  I only get one regular bump.


Le 20 oct. 2014 à 09:43, Magnus Danielson a écrit :

> Bob,
> 
> Since the satellite orbit the earth with a period of 11 hours and 58 minutes, it is actually twice a day.
> 
> Cheers,
> Magnus
> 
> On 10/20/2014 03:50 AM, Bob Camp wrote:
>> Hi
>> 
>> The GPS constellation repeats roughly once a day. It is not at all uncommon to have a “worst case” sattelite  geometry for a given antenna location. If you have one, it will repeat once a day and show up as a bump in the timing out of your GPS module. If you track long term data, it will / may / can keep you from getting to the sort of stability you would expect in the 100,000 second range. It’s one of the main reasons that things like GPSD-Rb’s lock up with time constants much longer than 100K seconds. Yes having a Cs or something similar helps a lot looking for this sort of thing.
>> 
>> Bob
>> 
>>> On Oct 19, 2014, at 9:26 PM, Bob Stewart <bob at evoria.net> wrote:
>>> 
>>> Hi Bob Camp,
>>> 
>>> 
>>> In your response to Chris, you said: "Once you have it “right” you really need to check it over a month or two to watch for GPS “once a day” issues. "
>>> 
>>> Could I ask you what you meant by these "once a day issues"?  Was this a general comment, or was it about something specific?  As you know I'm working on a GPSDO and am doing a lot of testing, so if there's something else I should be looking for, please let me know.
>>> 
>>> 
>>> Bob - AE6RV
>>> 
>>> 
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