GPS Receiver Operation?

The principal of GPS receiver operation is the process of triangulation from radio signal emitting satellites. Similar to using instruments to point at stars and record angles, both vertical and horizontal and known distances between two points on the earth’s surface to triangulate a position on earth except much easier. Basically two angles and the known distance of one leg allows the calculation of the other two legs distances and the third angle.

Instead of having to make a measurement between two points the GPS receiver measures distance to a minimum of three of the twenty four satellites by using the travel time of radio signals from the satellites. This requires very accurate electronic timing circuits which have only become available recently.

Along with distance, you need to know exactly where the artificial stars (satellites) are in space in order to extrapolate an angle from the Global Positioning System receiver position to them. GPS satellites are positioned in orbits high enough that their rate of forward speed matches their rate of fall and they are spaced around the earth so that no matter where you are at least three satellites can be acquired at the same time by the GPS. They are said to be in geosynchronous orbits, they stay in the same position relative to the earth as it rotates on its axis.

The twenty four satellites are essentially dumb radio transmitters. All the calculations are done in the GPS receiver which compares the code being transmitted from the satellites with its own internal code. The difference between the codes match times the speed of light equals the distance the GPS receiver is from each satellite. It compares the code differences between the signals from three or more satellites and resolves the distances to its actual location on earth..

The math equation is "velocity X travel time = distance" little more complicated then the problems we did in high school. In the case of GPS receiver it is measuring a radio signal so the velocity is going to be the speed of light or roughly 186,000 miles per second and the times are measured in millionths of a second.

The GPS receiver is an extremely accurate device and with it one can always know where they are and via the feature of being able to record location points - way points - and go back to them additionally one is never lost and can always return to a point which they have been and entered in the unit or have manually entered the coordinates of. You can, "if so inclined", give someone else the coordinates of your favorite deer stand, fishing hole or dive treasure, which they can enter in their unit and easily find.

There are several manufacturers of exellent gps receivers handheld and permanently mountable units for vehicles and boats.