How does a global positioning system work?

Answer 1

For the gps global position system, the satellites orbiting Earth is the basis. Each satellite orbits earth twice a day on one of six separate orbital paths. The Department of Defense created the system, which was originally for military purpose. In 1983, the civilians got the right to use the system after many practical application stem from its infrastructure.

All the satellites transmit the signals down to Earth in the global positioning system. Each satellite is programmed to send the signals at the same time. The signal contains the digital information about the satellite's identification and position. The information transmission time is very important. Each satellite is set up the time and the time is extremely precise. Your car's satellite gps receiver could receive the satellite transmissions if it has a clear view of the sky, not blocked by the solid object like building or mountains.

There should be a time difference form the signal was sent when the gps unit receivers the satellite signal. Because the signal need to take time to reach your receiver. But the receiver could automatically calculate the distance to the satellite by the simple formula of speed×time=distance. As the satellite transmissions all travel at the speed of light, which is already known.

You can not know where you are if you just know the distance to one satellite. The information just tell you that you are somewhere within a sphere around the satellite. So gps must use trilateration. The trilateration equates to using the distance to at least three satellites to determine your position. Three satellites could convey an accurate two-dimension fix, giving you your longitude and latitude coordinates, and four satellites give a three-dimension fix that includes elevation. Basically, the more satellites are used, the more accurate location is. Gps satellite orbits were designed in such a way that you will always have an effective, clear path to at least four satellites.

The coordinates is not very helpful when you are in a car. Nobody will use coordinates to give directions or to navigate highways and roads. This is the map software's use. It like a paper map, including the detailed information on the roadways and features of a given area. The map companies are constantly updating the digital maps to provide the most accurate mapping possible. The gps unit is able to overlay your location onto the map and provide turn-by-turn directions with the map data.