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CHAPTER 11 THE HYPERBOLIC SYSTEMS
The hyperbolic systems Decca and Omega have gone, but Loran-C, the
one terrestrial network providing extensive coverage, remains as the
designated back-up system to the GPS. By Presidential order, on 1 May
2000, Selective Availability, the method by which GPS accuracy was
downgraded for civilian users, was set to zero. This significant event
means that submetre accuracy position fixing is now available for all
users, a factor that will have a major impact on GPS equipment and
subsystems over the next decade.
© 2018 Digital Galaxy Index 121
