The Global Positioning System (GPS) is a satellite-based navigation system made up of a network of 24 satellites placed into orbit by the U.S. Department of Defense. GPS was originally intended for military applications, but in the 1980s, the government made the system available for civilian use. GPS works in any weather conditions, anywhere in the world, 24 hours a day. There are no subscription fees or setup charges to use GPS.

The 24 satellites that make up the GPS space segment are orbiting the earth about 12,000 miles above us. They are constantly moving, making two complete orbits in less than 24 hours. These satellites are travelling at speeds of roughly 7,000 miles an hour.

GPS satellites are powered by solar energy. They have backup batteries onboard to keep them running in the event of a solar eclipse, when there's no solar power. Small rocket boosters on each satellite keep them flying in the correct path.

Using GPS Signal

GPS satellites circle the earth twice a day in a very precise orbit and transmit signal information to earth. GPS receivers take this information and use triangulation to calculate the user's exact location. Essentially, the GPS receiver compares the time a signal was transmitted by a satellite with the time it was received. The time difference tells the GPS receiver how far away the satellite is. Now, with distance measurements from a few more satellites, the receiver can determine the user's position and display it on the unit's electronic map.

A GPS receiver must be locked on to the signal of at least three satellites to calculate a 2D position (latitude and longitude) and track movement. With four or more satellites in view, the receiver can determine the user's 3D position (latitude, longitude and altitude). Once the user's position has been determined, the GPS unit can calculate other information, such as speed, bearing, track, trip distance, distance to destination, sunrise and sunset time and more.
 
GPS Setup

GPS receiver needs to establish clear line of sight to receive signals from satellites orbiting in the space. If the receiver is placed inside a vehicle or vessel, an extended antenna is normally required to pick up signals beyond the enclosed area of the vehicle or vessel. GPS won't work indoor and its accuracy tends to degrade significantly when the receiver is located under sheltered area or near high-rise building structure or terrain.

Please note that various types of I/O interface exist among different types of pocket PC (even for the same brand), you should ensure that the output interface of the receiver is compatible with your pocket PC. Consult the technical specifications or device dealer of your receiver or pocket PC if you are in doubt about compatibility.

For Bluetooth GPS, you'll need to setup the connection between GPS receiver and your Device. Please follow the manufacturer instructions and be reminded to press ? Connect' of GPS device before you start using GPS.