Re: [Thumbgps-devel] [gpsd-dev] PPS over USB

[tz <tz2026@gmail.com>]

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SkyTraq has a different version of the 638 (not just different firmware)
that emits corrections to the pps edge to go to 10nS, and after a lock it
will work down to 1 satellite and maintain accurate pps.

I don't know of any others that retain pps if they don't have a 3d lock.

The antenna is important but it won't overcome an obscured view of the sky
- at best you will get multipath or other errors with the weak signals.
On May 1, 2012 11:33 PM, "Eric S. Raymond" <esr@thyrsus.com> wrote:

> Dave Taht <dave.taht@gmail.com>:
> > I'm a little confused.
> >
> > There are two threads going by today. One is about a sirfIII and the
> > other a ublox 6
> >
> > I have been assuming they are one and the same, but perhaps I'm confused.
>
> You are.  The first set of prototypes, from UniTraq, were SiRF-III +
> CP2101.
> These won't do - turns out the CP2101 driver can't wait on a handshake
> state
> change because the vendor never released enough programnming information.
>
> Gary is talking about the second set of prototypes, from NaviSys.
> That's the uBlox + PL2303 device.  It works.  The next step is to
> get them into volume production.
>
> > Secondly an item that has not been looked into much is the quality of
> > the antennas, or the quality of the clock source when only a single
> > sat is available....
>
> Quality of antenna will matter for the device's ability to function in
> weak-signal conditions, e.g. indoors.  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.
>
> > Thirdly, wow.... when can I get one of these puppies to play with?
>
> Gary has three.  He's keeping one and sending me the second.  Since OpenBSD
> has no TICMIWAIT, Chris Kuethe is out of contention for the third and it
> should logically go to you.
> --
>                <a href="http://www.catb.org/~esr/">Eric S. Raymond</a>
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