NAVSTAR Global Positioning System (GPS) Fact Sheet released by the Bureau of Oceans and
The NAVSTAR Global Positioning System (GPS) is a constellation of 24 satellites developed, launched, and maintained by the United States Air Force that provides positioning, timing, and navigation signals free of charge to both military and civilian users worldwide. GPS is the heart of a Global Navigation Satellite System (GNSS), which includes augmentation systems being developed by the United States, Europe, and Japan. In September 1998, President Clinton and Prime Minister Obuchi issued a joint statement on cooperation in the use of GPS. The United States and Japan will work together to promote and facilitate uses of GPS and cooperate on areas of mutual interest. The United States also has been holding discussions with the European Union on cooperation on GPS and GNSS. Europe currently is developing an augmentation system, EGNOS, which uses the GPS signal as its basis. Europe is debating its future direction for global navigation services. One possibility is to continue to use GPS and provide increased accuracy and integrity through EGNOS. The other direction under consideration is for Europe to develop its own constellation of global navigation satellites to provide a service similar to GPS. This development could be in partnership with other countries or an independent effort. The decision is expected during the first half of 1999. The United States believes that GPS, in combination with augmentation services such as the United States WAAS, European EGNOS, and Japanese MSAS, can satisfy user requirements. If Europe does elect to build its own system, the United States feels it would best serve the users throughout the world if any European system is interoperable with GPS and contributes to a seamless, transparent service. The United States feels that a European GPS-like system may be welcomed by many users and could potentially drive new applications. To that end, the United States and European Union have held five rounds of consultations in the last 2 years. The United States also is exploring its own methods of improving the service for the rapidly expanding number of civil users. U.S. actions include the provision of a second civil frequency, which was announced by Vice President Gore on March 30, 1998. Other improvements include the planned provision of a third civil frequency. In addition, the growing use of pseudolites is providing users additional signals for improved availability. Pseudolites are ground-based radio transmitters with a signal structure employing essential characteristics of the GPS satellite signals. They provide additional ranging signals and will be used in safety-critical applications such as aviation where a minimum level of navigation performance must be guaranteed. Other applications include land survey, mining, precision agriculture, vehicle navigation, harbor navigation, and docking for large vessels, such as high-speed ferries and oil tankers. Since pseudolites represent ground-based augmentations of the basic GPS service, commercial markets are expected to open very quickly.
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