How satellite navigation estimates your position
A satellite-navigation receiver compares the arrival times of signals from satellites whose positions are known. Those timings provide distance-related measurements. Typically, signals from at least four satellites let it solve for three-dimensional position and its own clock error, rather than simply drawing a triangle on a map.
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Timing becomes a distance estimate
Navigation satellites broadcast signals containing timing and orbital information. A receiver compares transmission and reception timing to estimate how far each signal travelled.
Its internal clock is not as accurate as the satellites' clocks. The measured ranges therefore include a shared clock-related error, often described using pseudoranges.
With enough satellite measurements, the receiver can solve for position and clock offset together. Four satellites typically provide the minimum for an unconstrained three-dimensional solution.
- Satellite information establishes reference positions.
- Signal timing supplies range-related measurements.
- The receiver solves the resulting set of constraints.
Buildings and other surfaces can reflect signals, increasing error. A basic satellite-navigation fix does not require the receiver to send its location to a satellite, although connected services can provide assistance and additional data.