[ntp:questions] SIRF time output wobble, GPS or NTP fault?
albertson.chris at gmail.com
Tue Mar 6 21:03:28 UTC 2012
On Tue, Mar 6, 2012 at 11:30 AM, David J Taylor
<david-taylor at blueyonder.co.uk.invalid> wrote:
> "unruh" <unruh at invalid.ca> wrote in message
> news:Obt5r.32277$HR6.15856 at newsfe21.iad...
>> Since a 1 second error in nmea would also impact the PPS output, his
>> observation is far from irrelevant. That was what happened with the
>> Garmin 18x-- the nmea offset became greater than a second, and all hell
>> broke out.
> So you agree with me, that the NMEA output is not to be trusted. However,
> it should not be an issue in a GPS designed and specified for timing
> purposes, and working to specification.
Are there any NMEA GPS that are designed for timing? Maybe - but I
can't think of one right now.
I think the GPS could be working within its specs and still be as far
off as was reported. The spec only requires that NMEA data to be
output within the second to which they apply. The worst case reported
error as about 0.9 seconds which is within spec.
Redondo Beach, California
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