100 Years of Relativity Space-Time Structure: Einstein and Beyond ...

288 N. Ashbymercial, private, and military use. The number of receivers manufacturedeach year is in excess of two million, and different applications are continuallybeing invented. Marketing studies predict that sales of GPS equipmentand services will grow to over $34 billion by 2006. Revenue for the EuropeanGALILEO system is projected to be 10 billion Euros per year.12. ConclusionsThe GPS is a remarkable laboratory for applications of the concepts of specialand general relativity. GPS is also valuable as an outstanding sourceof pedagogical examples. It is deserving of more scrutiny from relativityexperts. It is particularly important to confirm that the basis for synchronizationis on a firm conceptual foundation.References1. Fliegel, H. F., and R. S. DiEsposti, “GPS and Relativity: an EngineeringOverview,”, Aerospace Corp. Report No. ATR-97(3389)-1, 20 Dec. (1996).2. Malys, S., and Slater, “Maintenance and Enhancement of the World GeodeticSystem 1984,” Proc. ION-GPS-94, Salt Lake City, UT, Sept. 20-23,1994, pp 17-24 (1994); National Imagery and Mapping Agency TechnicalReport 8350.2, “World Geodetic System 1984,” Third Edition, Amendment1, NIMA Stock No. DMATR83502WGS84, NSN 7643-01-402-0347.3. Ashby, N., and Weiss, M., “Global Positioning Receivers and Relativity,”NIST Technical Note 1385, U. S. Government Printing Office, Washington,D.C., March (1999).4. Ashby, N., ”An Earth-Based Coordinate Clock Network,” NBS TechnicalNote 659, U. S. Dept. of Commerce (1975). U. S. Government PrintingOffice, Washington, D.C. 20402 (S. D. Catalog # C13:46:659).5. Allan, D.W., Ashby, N., and Weiss, M., Science 228, 69–70, (1985).6. See http://www.danof.obspn.fr/IAU Resolutions/Resol UAI.htm for resolutionsadopted at the 20th General Assembly, Manchester, August 2000.7. Lambeck, K., Geophysical Geodesy, Oxford Science Publications, TheClarendon Press, Oxford pp 13-18, (1988).8. Ashby, N., and Spilker, J.J., Jr., “Introduction to relativistic effects on theGlobal Positioning System,” Chapter 18 in Parkinson, B.W., and Spilker,J.J., Jr., eds., Global Positioning System: Theory and Applications, Vol.I, American Institute of Aeronautics and Astronautics, Inc., Washington,D.C., pp 623-697 (1996).9. Garland, G.D., Earth’s Shape and Gravity, Pergamon Press, New York(1965).10. Ashby, N., and Allan, D.W., “Practical Implications of Relativity for aGlobal Coordinate Time Scale,” Radio Science 14, 649-669 (1979).11. Fitzpatrick, P., The Principles of Celestial Mechanics, Academic Press, NewYork (1970).