GPS-the necessity of the outdoor games

The Blobal Positioning System is composed of the 24 satellites, group control station and countless receivers-the user terminal. The powerful system is established in 1973. It began launching the satellite in 1989. It's completed until 1994. The "GPS" we generally mention is only thegps personal tracker which we have in hand. Actually, the GPS is a very powerful system.

How does the GPS work? The 24 GPS satellites send out the location and time information by the means of radio cast. When the GPS recieves the signal of the satellite, it will carry out the calculation based on its own clock information and the clock and location information of the satellite. What's the result? It's worked out to be the distance between the GPS and the satellite.

Theoretically, if the GPS receives the signals from more than three satellites and the distances to the three satellites have been worked out, the coordinate figures can be gained. The position can be achieved. If it receives more satellite signals, the more exact coordinate figures can be gained. Thus, to achieve an exact location, the clear satellite signal should be gained.

As to the existed technology, the modified positioning accuracy can reach the millimeter. It's like the broadcast station to the radio. As the GPS satellites send out the signal as the broadcasting, you can receive the signal with a radio. The company running on the GPS system will charge the users directly.

The system will create the direct benefit in the production. The GPS technology standard is also sold. Then others can also produce and use the GPS device. The technology permission fee will be charged from the manufacturer. When you buy a GPS, you hand in the money.

It's also different from the relation between the broadcast station and radio. The GPS is one way communication. The GPS device is unable to communicate with the satellite itself. The satellite and the ground station have no knowledge of the location of the GPS receiver. It's not real to track the car or criminal with the satellite tracker. It's only showed in the movie. In other words, it's not relied on the GPS system.

At present, a practical GPS tracker is realized by a GPS receiver and a sim card. That's to say the receiver is responsible for the location. The positioned signal will be sent out by message. The GPS receiver itself is a dummy. It can't tell the location. We mentioned above that the accuracy can reach the millimeter level. It's possible that some people can't understand it. Why can't my model reach it? The critical parts of the GPS including the satellite, ground control station and the whole technology are made in US. So the regulation is decided by American people.

One day in 1992, the American told all the users, "For the sake of the national security, I won't offer you the exact signal." Then they added the S/A interference code. As the code is availabe, except for the special authorized user, the positioning accuracy of the others has plummeted.