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Suggested Citation:"Inmarsat." National Research Council. 1995. The Global Positioning System: A Shared National Asset. Washington, DC: The National Academies Press. doi: 10.17226/4920.
Page 173

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APPENDIX C 173 and is compiling information on maritime DGPS broadcasts worldwide. Currently Sweden, Finland, The Netherlands, Denmark, Iceland, and Germany have complete or nearly complete coastal coverage. Several other countries have prototype or demonstration services including Australia, Canada, China, Norway, and Poland. India and South Africa are planning maritime DGPS services. International Participation in the FAA's WAAS In order to eventually develop the WAAS into a Global Navigation Satellite System (GNSS) that is useful to aircraft anywhere in the world, the FAA is encouraging other nations to participate in the program at any level they feel comfortable with.56 Nations involved at the lowest level will simply utilize the GPS-like WAAS signals without any contribution to the system in the form of ground based wide-area reference stations. Participation at a higher level would involve the installation of wide-area reference stations and possibly wide-area master stations within the sovereign territory of a nation. Even higher levels of involvement are possible if a nation is willing to provide a geostationary satellite for the space segment of the system. Several countries have expressed an interest in WAAS participation, including Canada, Australia, New Zealand, and Japan.57 Inmarsat Inmarsat (the International Maritime Satellite Organization), a not-for-profit international organization that provides global mobile satellite services to the maritime, land- mobile, and aviation markets, has firm plans to augment GPS by placing a navigation payload on board its third generation geostationary communications satellites. Plans call for this payload to broadcast GPS and GLONASS integrity information, ranging information, and wide-area differential corrections on a "GPS-like" L1 signal centered at 1575.42 MHz. These satellites and their navigation payloads may form the nucleus of the WAAS space segment if the winning team of contractors chooses to use them. Future Inmarsat plans include the possible development of a fully civil GNSS based on light satellite (lightsat) navigation payloads placed in intermediate circular orbits and geostationary orbits.58 56 Robert Loh, "Worldwide Seamless WAAS Concepts," Viewgraphs presented at the 1995 National Technical Meeting of the Institute of Navigation, Anaheim, California, 18-20 January 1995. 57 Japan has already established firm plans to develop two geostationary satellites known as the multifunctional transport satellites (MTSAT's) that will augment GPS air navigation in the Asia/Pacific region. These satellites and their ground monitoring network could potentially become part of WAAS. 58 Jim Nagle, "Waypoints to Radionavigation in the 21st Century," Viewgraphs presented to the National Academy of Public Administration (NAPA) Panel on GPS, 18 November 1994.

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The Global Positioning System (GPS) is a satellite-based navigation system that was originally designed for the U.S. military. However, the number of civilian GPS users now exceeds the military users, and many commercial markets have emerged. This book identifies technical improvements that would enhance military, civilian, and commercial use of the GPS. Several technical improvements are recommended that could be made to enhance the overall system performance.

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