How does GPS determine a position?

Triggered by a very precise clock in the satellite, an electromagnetic signal is sent out at specific intervals. This signal contains information about the time and position of the corresponding satellite at the exact time of transmission. A GPS receiver reached by this signal has an equally precise clock and is therefore able, from the running time of the signal, to calculate the distance to the satellite. This yields the first piece of information used for determining the position, located on an arc that runs across the earth's surface. The utilization of another signal (another satellite) leads to an intersection of two arcs, and a pinpointing of location. Necessary for this kind of signal evaluation is the high precision clock in the receiver, like that of the satellite. That one is able to do without a high precision, long term stable and therefore expensive clock in the receiver, is made possible by a further measurement by a third satellite, of the time difference between the ...  more