Global positioning system (GPS)

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Case study notes^[1]

Introduction[edit]

A GPS satellite:

The GPS constellation of satellites consists of at least 24 satellites – 21 primary satellites and 3 orbiting spares. They orbit the earth at an altitude of 17,500 KM (10,900 miles) at a speed of 1.9 miles per second between 60°N and 60°S latitude. Each satellite weighs 1900 lbs and is 17 feet (5.81 meters) wide with solar panels extended. The satellites orbit the earth twice a day. This guarantees that signals from six of the satellites can be received from any point on earth at almost any time. The global coverage is 24 hours a day, all weather conditions.

The Global Positioning System (GPS): was designed for military applications. Its primary purpose was to allow soldiers to keep track of their position and to assist in guiding weapons to their targets. The satellites were built by Rockwell International and were launched by the U.S. Air Force. The entire system is funded by the U.S. government and controlled by the U.S. Department of Defense. The total cost for implementing the system was over $12 billion.

Presently the system is right now open for everyone to use it. The only condition is to have a GPS device for e.g.

How does it work[edit]

The position of a user is calculated by measuring the distance to three/four satellites, taking the point of intersection in a process called trilateration. In order for this to work, each satellite carries an atomic clock so that the distance between the GPS receiver and the GPS satellite can be calculated through exact time differences.