On Feb 23, 5:15 pm, doug <x...@xx.com> wrote:
> koobee.wub...@gmail.com wrote:
> > On Feb 23, 12:01 pm, Eric Gisse wrote:
>
> >>On Feb 23, 9:49 am, koobee.wub...@gmail.com wrote:
>
> >>>You need four satellites where each satellite should know its time and
> >>>position.  Time can just be a counter with all the satellites
> >>>synchronized to within a count of each other.  Each satellite then
> >>>just broadcast its time and position information as almanac signal to
> >>>whoever wants to receive it.
>
> >>>Since the distance is traveled by light with a known speed, you can
> >>>then easily form a set of four equations with four unknowns.  The four
> >>>unknowns are your time (relative to the counter in each satellite) and
> >>>position.
>
> >>>**  c^2 (t1 – t)^2 = (x1 – x)^2 + (y1 – y)^2 + (z1 – z)^2
> >>>**  c^2 (t2 – t)^2 = (x2 – x)^2 + (y2 – y)^2 + (z2 – z)^2
> >>>**  c^2 (t3 – t)^2 = (x3 – x)^2 + (y3 – y)^2 + (z3 – z)^2
> >>>**  c^2 (t4 – t)^2 = (x4 – x)^2 + (y4 – y)^2 + (z4 – z)^2
>
> >>>Where
>
> >>>**  (t1, x1, y1, z1) = Time and position of satellite 1
> >>>**  (t2, x2, y2, z2) = Time and position of satellite 2
> >>>**  (t3, x3, y3, z3) = Time and position of satellite 3
> >>>**  (t4, x4, y4, z4) = Time and position of satellite 4
> >>>**  (t, x, y, z) = Time and position of the receiver
>
> >>>Notice that relativistic effect is never needed.
>
> >>...even tnough t1-4 are wrong by roughly 50,000ns/day?
>
> > So, the college drop-out sleeps until 11AM Alaska time today.
>
> > In the meantime, if t1 is off by 50usec a day relative to the ground,
> > as long as t2, t3, and t4 are all off by the same amount, it does not
> > matter.  There is still no need for any relativistic correction.
> > <shrug>
>
> Of course the relativitistic correction is needed. The satellites
> get their location information from the ground. They need to know
> the times for that.  Read about how the gps works.- Hide quoted text -
>
> - Show quoted text -

Tracking Geosynchronous Satellites with GPS

The traditional method of orbit determination for a geosynchronous
spacecraft is to collect occasional range measurements from a tracking
station on the ground. More than one station might be used, but never
more than one at a time. Scientists have known this approach would be
improved by adding more tracking stations and positioning them as far
apart as possible along the circumference of Earth (as seen by the
satellite). Unfortunately, many factors make this arrangement
impossible. GPS offers a simpler solution.

Viewed from a geosynchronous spacecraft, GPS satellites (on the
opposite side of Earth) are positioned somewhat beyond the edge of the
planet—providing better tracking geometry than would be possible from
any location on the ground. Moreover, the orbital configuration of the
GPS constellation ensures that various satellites will be seen at
comparatively wide distances from each other, further improving the
tracking geometry. Also, in comparison to ground-based stations, GPS
satellites exhibit greater relative motion with respect to the
geosynchronous satellite.

Of course, a geosynchronous satellite will rarely, if ever, have four
GPS satellites in view. Thus, it cannot employ GPS signals the way a
user on Earth would. But geosynchronous satellites only use one
station in their traditional method of orbit determination anyway, so
an absence of more GPS signals is not a deficit.
 This answers my question I understand the difference for applications
of them not being  Geosynchronous GPS Satellites