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Re: [gpsd-dev] PPS over USB
From: |
Eric S. Raymond |
Subject: |
Re: [gpsd-dev] PPS over USB |
Date: |
Sun, 6 May 2012 17:28:43 -0400 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
Hal Murray <address@hidden>:
>
> address@hidden said:
> > Clock time should be OK even with a single sat - multiple birds are needed
> > for the spherical trig to compute position, but atomic time you get directly
> > from each sat sample.
>
> I think it's more complicated than that.
>
> You can get time with only 1 sat if know where you are located. It takes
> special software, usually called "timing".
That's if you care about precision to less than the variation in
lightspeed-from-orbit and ionosphere delays. Physicists do; most
other people don't, which is why uBlox can sell a device with a
time-service mode that (as I read the datasheet) doesn't require
a pre-survey.
Theoretical discussion only, since most GPses won't report time
without a (3-sat) fix and GPSD doesn't
> It's worth asking Navisys if they have the timing mode software.
No chance. I can ask, but I'm certain they'll not evenn know it exists.
--
<a href="http://www.catb.org/~esr/">Eric S. Raymond</a>
- Re: [gpsd-dev] PPS over USB, (continued)
- Re: [gpsd-dev] PPS over USB, Jim Thompson, 2012/05/01
- Re: [gpsd-dev] PPS over USB, Eric S. Raymond, 2012/05/01
- Re: [gpsd-dev] PPS over USB, Hal Murray, 2012/05/02
- Re: [gpsd-dev] PPS over USB, Jim Thompson, 2012/05/02
- Re: [gpsd-dev] PPS over USB, Gary E. Miller, 2012/05/02
- Re: [gpsd-dev] PPS over USB, Chris Kuethe, 2012/05/02
- Re: [gpsd-dev] PPS over USB, Dave Taht, 2012/05/02
- Re: [gpsd-dev] PPS over USB, HÃ¥kan Johansson, 2012/05/02
- Re: [gpsd-dev] PPS over USB, Gary E. Miller, 2012/05/02
- Re: [gpsd-dev] PPS over USB, Chris Kuethe, 2012/05/02
- Re: [gpsd-dev] PPS over USB,
Eric S. Raymond <=
- Re: [gpsd-dev] [Thumbgps-devel] PPS over USB, tz, 2012/05/02
- Re: [gpsd-dev] [Thumbgps-devel] PPS over USB, Gary E. Miller, 2012/05/02
- Re: [gpsd-dev] [Thumbgps-devel] PPS over USB, tz, 2012/05/02
- Re: [gpsd-dev] [Thumbgps-devel] PPS over USB, Hal Murray, 2012/05/02
- Re: [gpsd-dev] [Thumbgps-devel] PPS over USB, tz, 2012/05/02
Re: [gpsd-dev] PPS over USB, Ed W, 2012/05/04