3 Answers

  • 2 months ago

    Each GPS satellite has an atomic clock onboard, an ultimately accurate time reference.

    They all broadcast their identities and the time from their clocks.

    They also regularly send the GPS satellite array orbital parameters (keplers) which allows a GPS receiver to plot the exact location in space of every satellite relative to the Earth and each other.

    That in turn allows the GPS receiver to calculate its distance from each satellite it can pick up, by the time the signal takes to get to it from the satellite. 

    By cross referencing that with the satellite locations, it can work out its own location.

    It needs to be able to receive three satellites to get a 2D ground location; with four or more it can calculate a 3D location fix with altitude as well.

    The more it can receive without noise or interference (like reflections from buildings) the more accurate the location it can plot.

    To be able to measure the time delay in receiving the satellite signals, the receiver itself has clock accurate accurate to nanoseconds or even picoseconds, set via the timing signals it receives.

    Some types or receiver have a separate timing output signal that pulses once a second (PPS), with the start of the pulse accurate to typically 50 picoseconds on a reasonable quality one.

    Those are often used as time standards, such as synchronising the time of internet systems around the world.

  • Anonymous
    2 months ago

    It's a process of triangulation. The GPS satellites know exactly where they are and what time it is, and send a coded signal to be picked up by the receiver in your device. Knowing the time the signal was sent and the speed of light, the device can figure out how far away from the satellite it is, and know that it's somewhere along a circle traced on the Earth. By reading a second, third and fourth satellite it can narrow its location down to where those circles (spheres actually) intersect.

  • Rick
    Lv 7
    2 months ago

    there are a number of different satellites circling the Earth in stable orbits all transmitting a different signal, and the 'receivers' get those different signals and plot there locations ......

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