The Global Positioning System: Assessing National Policies,

The Global Positioning System GPS is a U.S. military space system operated by the U.S. Air Force. The space segment of GPS consists of a constellation of 24 satellites that broadcast precise time signals. When the satellites are in view of a suitable GPS receiver, these signals aid position-location, navigation, and precision timing. GPS was developed by the U.S. Department of Defense and deployed over two decades at a cost of over 10 billion. The U.S. armed forces are increasingly reliant on its signals for a variety of purposes from navigation to munitions guidance. However, over the past 10 years, GPS has evolved far beyond its military origins. It is now a worldwide information resource supporting a wide range of civil, scientific, and commercial functions, from air traffic control to the Internet. GPS has also spawned a substantial commercial industry in the United States and abroad with rapidly growing markets for related products and services.