Overview

The global positioning system is a location determination network that use satellites to act as reference points for the calculation of position information. GPS is used in civilian and military products.

There are several systems used for global positioning. These include the United States global positioning system (GPS) system, the Russian Global Navigation Satellite System ( GLONASS ), and the European Galileo system.

In the late 1980 s, the military began to allow GPS technology to be used for public use. Due to the much larger number of units in production, the price for GPS equipment was dramatically reduced. Because the government maintains the satellites, there is no cost to use GPS service.

The US GPS system is based on 24 orbiting satellites and is called NAVSTAR. GPS receivers can calculate their exact location (height and location or longitude and latitude) by measuring the distance from four or more satellites. Consumer devices are accurate within one city block and commercial/military devices can measure to the millimeter (less than 1/16 inch). With the addition of software grid information, a real-time driving location map can be generated and available to those people who never get lost .

Figure 1 shows a global positioning satellite (GPS) system. This diagram shows how a GPS system receives and compares the received time from orbiting GPS satellites to determine its geographic position. Using the precise timing signal based on a very accurate clock, the GPS receiver compares these signals from 3 or 4 satellites. Each satellite transmits its exact...