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Topic: GPS math
Replies: 1   Last Post: Feb 9, 2013 7:46 PM

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Posts: 419
Registered: 10/7/06
Re: GPS math
Posted: Feb 9, 2013 7:46 PM
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On Feb 9, 3:06 am, "Jon" <> wrote:
> Here is GPS math with an embedded spreadsheet to calculate solutions:
> There is some argument about calculating distances from the GPS receiver and
> the 3 satellites.  The solution to this is the satellites send a time stamp
> with their signal.  Consequently the only atomic clocks required are on
> board the satellites themselves and not on every receiver.  At that the
> satellites need only be updated by an atomic clock.  This is how distances
> are calculated.  Once they're determined, the GPS coordinates can be found
> with just the coordinates of the satellites.  This web page I made shows
> how.

You can't find a solution with three satellites only, because you
don't know the distance to any receiver.

The time stamp on the signal doesn't give you the distance from
receiver to satellite, because you don't know the time of the

If you have two time stamps from satellites A and B, then you now the
_difference_ between the distance RA and the distance RB (distance
from receiver to point A or B), but not either distance. With four
timestamps from four satellites you can determine your position.

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