On Feb 23, 2:54 pm, torso <sgwt...@count.com> wrote:
> On Feb 23, 11:40 pm, Dono <sa...@comcast.net> wrote:
>
>
>
>
>
> > On Feb 23, 12:33 pm, Cephalobus_alie...@comcast.net wrote:
>
> > > On Feb 23, 12:49 pm, koobee.wub...@gmail.com wrote:
>
> > > > On Feb 20, 4:33 am, "Jon" <jon8...@peoplepc.com> wrote:
>
> > > > > Supposing three satellites transmit signals with time stamps that are picked
> > > > > up by a receiver.  If the clocks on the satellites are closely synchronized,
> > > > > then
>
> > > > > |AD|=|AB|+t_AB
> > > > > |BD|=|BC|+t_BC
> > > > > |CD|=|CA|+t_CA
>
> > > > > Where
> > > > > A,B,C=position vectors of three satellites
> > > > > AB,BC,CA=distances between satellites
> > > > > t_AB,t_BC,t_CA=time differences between signals at D.
> > > > > D=position vector of receiver.
>
> > > > > Once |AD|,|BD|,|CD| are found, the coordinates of D can be derived.
>
> > > > > Is this how it is done?
>
> > > > > summarized at
>
> > > > >http://mypeoplepc.com/members/jon8338/math/id8.html
>
> > > > 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.
>
> > > Currently, only Block IIR satellites are capable of autonomous
> > > position monitoring and synchronization independent of the ground
> > > control segment. This capability allows Block IIR satellites to
> > > mutually correct their clocks and ephemerides information for a
> > > period of up to several months should the ground segment be
> > > knocked out by, say, nuclear war. For optimum performance under
> > > non-wartime conditions, "ground truth" comparisons are still
> > > performed on a daily basis to correct the satellites for drift.
>
> > > GPS satellites before the Block IIR series are incapable of such
> > > mutual correction, and require monitoring and daily corrections
> > > by the Ground Segment.
>
> > > Satellite control requires that the Space Segment and Ground
> > > Segment clocks be synchronized. The only practical way of
> > > synchronizing the world-wide network of ground stations is to
> > > use the network of GPS satellites to disseminate time. The only
> > > way to use the networks of GPS satellites to disseminate time is
> > > if the satellite clocks are adjusted via the GR correction so
> > > that they beat in time with Earth clocks.
>
> > > Jerry- Hide quoted text -
>
> > > - Show quoted text -
>
> > Jerry
>
> > According to Dave's post (see above), the satellites in relative
> > motion (at about 6.7km/s) so the Kobee-Wublee idiot needs to
> > understand that, even with Block IIR, the relativistic corrections are
> > still needed.
>
> i thought they were geostationary- Hide quoted text -
>
> - Show quoted text -

Ahh, the Australian fake idiot :-)