koobee.wublee@gmail.com wrote:
> On Feb 23, 8:00 pm, <b...@bla.org> wrote:
>> 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.
>> The last statement is not true, a relativistic effect must be considered
>> in GPS because you're dealing with a space based clock that travels at
>> several km/s relative to an observer on Earth. Furthermore there is a
>> difference in the gravitational potential between Earth and the GPS
>> satellite so that you need the GR correction as well.
> 
> Hmmm...  You never understood what I said and what the Wikipedia
> article said below.  <shrug>
> 
> http://en.wikipedia.org/wiki/Gps

Just look under the section relativity, it is explained there.

> 
>> [Rest of nonsense snipped]


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