The Global Positioning System involves the use of transmission of at least 4 radio wave signals from a "constellation" of 24 earth-orbiting satellites at one time.A Global Positioning System (GPS) unit consists of a space segment, a control segment, and a user segment. The space segment is a constellation of two-dozen satellites orbiting the earth twice every 24 hours, at approximately 10,900 nautical miles above the earth's surface. The control segment is a series of monitoring stations located at different sites on earth. These stations update and correct errors in the navigational message of the satellites. The user segment is a receiver that receives radio waves from the satellites ...view middle of the document...
A fourth satellite is used to confirm the target location. We also have to be outside in a fairly open area for the GPS receiver to work.If it does work, the receiving unit uses triangulation to calculate extremely accurate measurements of the user's position, velocity and time. This is accurate enough to potentially allow an aircraft to make a safe landing on a fog-bound runway, guided only by the GPS, or be used to measure the sluggish drift of the continents. If there is several receivers scattered everywhere, then the accuracy of a GPS can be narrowed down to 5-10 metres.GPS can also be used to measure distance. At a particular time (let's say midnight), the satellite begins transmitting a long, digital pattern called a pseudo-random code. The receiver begins running the same digital pattern also exactly at midnight. When the satellite's signal reaches the receiver, its transmission of the pattern will lag a bit behind the receiver's playing of the pattern.The length of the delay is equal to the signal's travel time. ...
