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Re: [gpsd-dev] NMEA time calculation question
From: |
Gary E. Miller |
Subject: |
Re: [gpsd-dev] NMEA time calculation question |
Date: |
Mon, 7 May 2012 10:48:42 -0700 |
Yo Ed!
On Mon, 07 May 2012 16:44:36 +0100
Ed W <address@hidden> wrote:
> Hi, Could Eric or similar give me a confirmation on the current gpsd
> nmea time calculation?
I'll try.
> My understanding is that you take the final GPZDA sentence, then work
> *back* the timestamp of the initial $ by counting the number of
> characters divided by baud rate?
Nope, nothing anywhere near so fancy. And since the start of gps
sentences is so jittery there is no point to trying except for a
few special case GPS.
> Granted NMEA time is not traditionally considered incredibly
> accurate, but *if* the calculation is as I describe above, then we
> could potentially increase measurement accuracy by 0.5-1ms?
Right now the NMEA uncertainly is 70 milliSec or much worse. 1 milliSec
is noise.
> The reason for asking is that my Venus6 + CP210x has NMEA time that
> appears to measure almost as accurately as a theoretical PPS over
> USB.
Until the CP210x kernel driver is fixed there is no point thinking about
any usage of CP210x for timing.
RGDS
GARY
---------------------------------------------------------------------------
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97701
address@hidden Tel:+1(541)382-8588
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- [gpsd-dev] NMEA time calculation question, Ed W, 2012/05/07
- Re: [gpsd-dev] NMEA time calculation question, tz, 2012/05/07
- Re: [gpsd-dev] NMEA time calculation question, Jim Thompson, 2012/05/07
- Re: [gpsd-dev] NMEA time calculation question, Ed W, 2012/05/07
- Re: [gpsd-dev] NMEA time calculation question, tz, 2012/05/07
- Re: [gpsd-dev] NMEA time calculation question, Ed W, 2012/05/07
- Re: [gpsd-dev] NMEA time calculation question, tz, 2012/05/07
- Re: [gpsd-dev] NMEA time calculation question, Ed W, 2012/05/07
- Re: [gpsd-dev] NMEA time calculation question, tz, 2012/05/07
Re: [gpsd-dev] NMEA time calculation question,
Gary E. Miller <=
- Re: [gpsd-dev] NMEA time calculation question, tz, 2012/05/07
- Re: [gpsd-dev] NMEA time calculation question, Ed W, 2012/05/07
- Re: [gpsd-dev] NMEA time calculation question, tz, 2012/05/07
- Re: [gpsd-dev] NMEA time calculation question, Gary E. Miller, 2012/05/07
- Re: [gpsd-dev] NMEA time calculation question, Ed W, 2012/05/07
- Re: [gpsd-dev] NMEA time calculation question, Gary E. Miller, 2012/05/07
- Re: [gpsd-dev] NMEA time calculation question, Hal Murray, 2012/05/07
- Re: [gpsd-dev] NMEA time calculation question, Ed W, 2012/05/08
Re: [gpsd-dev] NMEA time calculation question, Hal Murray, 2012/05/07