How It Works
What is GPS?
A Brief History

History and Development
Initiated in 1973, the Global Positioning System (GPS), formally known as the Navstar Global Positioning System, was designed as a dual-use system with the primary purpose of enhancing the effectiveness of U.S. and allied military forces. Today, GPS is also rapidly becoming an integral component of the emerging Global Information Infrastructure with applications ranging from mapping and surveying to international air traffic management and automatic vehicle location (AVL).  

GPS has 3 parts: the space segment, the user segment, and the control segment. The space segment consists of 24 satellites, each in its own orbit 11,000 nautical miles above the Earth. The user segment consists of receivers, which you can hold in your hand or mount in your car. The control segment consists of ground stations (five of them, located around the world) that make sure the satellites are working properly.

How GPS Works
GPS is the only system today able to show you your exact position on the Earth anytime, in any weather, anywhere. GPS is accurate to within approximately 150 feet, but in practice accuracy is often far more precise, usually within 25 feet or less. GPS tracking satellites are continuously monitored by ground stations located worldwide. The satellites transmit signals that can be detected by anyone with a GPS receiver. Using the receiver, you can determine your location with great precision.

Military Uses for GPS
Although the GPS satellite constellation was completed only recently, it has already proved to be a most valuable aid to U.S. military forces. GPS has become important for nearly all military operations and weapons systems. In addition, it is used on satellites to obtain highly accurate orbit data and to control spacecraft orientation.

GPS Uses in Everyday Life
  • Fleet Vehicle Management: GPS Fleet vehicle tracking systems are being used by commercial and private trucking companies tracking cars, trucks, buses and other equipment.
  • Emergency management: Dispatchers for police, fire, and emergency medical service units use GPS vehicle tracking systems to determine which police car, fire truck, or ambulance is nearest to an emergency.
  • Consumer vehicles: GPS technology is being used as a theft recovery solution as well as for in-vehicle navigation systems.
  • Wildlife management: scientists use to track population patterns.
  • Engineering: used to help ensure the two ends of the tunnel between England and France met.
The future of GPS is as unlimited as your imagination. New applications will continue to be created as the technology evolves.

AVL and GPS - What's the difference?
AVL stands for Automatic Vehicle Location. Any system that uses technology to locate the position of vehicles (rather than data collected by human interaction) could be classified as AVL. GPS is one specific way to locate vehicles and is often part of a GPS vehicle tracking subsystem of a larger fleet management application.