Each satellite makes two complete orbits in a day - passing an area of the globe once every 12 hours. Communication with a GPS satellite by radio allows the ground-satellite transit to be a simple ranging action. Adjustments for various factors improves the quality of location. Since the particular satellite's position is also known, the length of the signal vector is established. This in effect results in a virtual sphere of space defined by the vector length.
Location now becomes a straightforward problme in triangulation.
This closes the first part of this Section.