Impact of the Cessation of Selective Availability (SA) on the Need 
for an Integrated Backup System

The International Loran Association -- May 2000
 
The International Loran Association (ILA) welcomes the cessation of SA. However, the discontinuance of SA has no effect on the fundamental principles and positions the ILA continues to advocate for all nations, applications, and individuals. Those principles and positions are restated below.
I The cessation of SA is beneficial for two primary reasons:
    • The accuracy of the global positioning satellite system (GPS) and of differentially corrected GPS is improved for marine, terrestrial, aviation, and timing applications for individual, commercial, and government applications – in whatever country they are utilized. 
    • The uncorrected or corrected GPS signal becomes a more accurate calibration source to improve the accuracy and performance of integrated backup systems. Integrated systems are necessary to ensure safe, reliable, and independent operations can continue whenever GPS is lost because of man-made interference (intentional or unintentional), natural interference, system failure or US government actions.
II The discontinuance of SA is irrelevant to the fundamental limitations and risks of a sole-means radionavigation system – i.e. no individual, business, or nation should place safety of life and transportation/commerce/telecommunications infrastructure on a single system. Dangers associated with reliance on a single system are exacerbated when it is space borne and subject to interference, system failure, and control by a single state.
III Therefore, the ILA remains committed to the following principles and positions:
    • All nations should use at least two systems that can function autonomously, with a minimum of one system under regional or national control. Only through use of such integrated systems will system reliability and the associated safety and continuity of performance attain the levels needed by countries desiring independent development and control of vital infrastructures. 
    • Systems combined to eliminate sole-means risks should be dissimilar to avoid common failure modes. 
    • Loran is an excellent complement to GPS and other satellite systems for many reasons:
      • Loran and GPS are synergistic, i.e. combining GPS and Loran results in a hybrid system with greater accuracy, availability, and integrity than either system alone.
  • Loran is multimodal, i.e. it can be used to complement/backup satellite systems in virtually every application associated with critical transportation, commerce, and telecommunications infrastructures, including marine, aviation, terrestrial, and timing.
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  • Loran is dissimilar to satellite systems: terrestrial versus space based, high signal strength versus low signal strength, low frequency versus high frequency, and regional control versus single state control.
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  • Loran infrastructure is remarkably inexpensive, reliable, and proven.
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  • Loran and satellite systems are multimodal, and therefore, economies of scale will ensure users get extremely price competitive products from numerous sources.
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    IV In summary, basic ILA principles and positions remain unchanged by the cessation of SA. The enhanced accuracy of GPS does not affect personal safety, system reliance, commercial and national vulnerabilities inherent in a sole-means system. Loran remains necessary and represents the best backup and complement to satellite systems for numerous safety, performance, economic, and political reasons.
    *** 
    Prepared by G. Linn Roth, Ph.D., May, 2000 while serving as President, International Loran Association