> Warner Losh wrote:
> >
> > What I was trying to say was that SA is caused by the satellites
> > reporting times that have a small offset added to or subtracted from
> > them. Knowing where you are requires that you know what time it is to
> > a very precise degree. Once you know what time it is, you can know
> > where you are. That's why SA injects a pseudo random noise factor
> > into the timing information that the satellites report. If you have
> > an atomic clock and a GPS clock, you can measure the offset between
> > the two fairly easily and graph the results. That is what I mean when
> > I say you can compensate for the SA if you have a good atomic clock.
>
> This is what "Differential GPS" provides: a standard time source that
> can be used to remove the SA meanderings from the GPS fix.
Indirectly; the actual differential GPS corrections provide pseudo-range
corrections. That is, the difference between what the actual distance
to the satellite is at the reference station, and the distance you
derive from the signal after it's been degraded. These days, thats
primarily ionospheric effects.
To Unsubscribe: send mail to [EMAIL PROTECTED]
with "unsubscribe freebsd-hackers" in the body of the message
