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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="";>Eric S. Raymond</a>

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