Service provided to gps users the us government will

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Unformatted text preview: event. Page 15 October, 2001 GPS SPS Performance Standard (INTENTIONALLY BLANK) Page 16 October 2001 GPS SPS Performance Standard APPENDIX A GPS Documented Performance Characteristics SECTION A-1 Introduction GPS performance behavior is dynamic, given the use of satellites as “mobile beacons”. GPS performance may however be defined in a straightforward fashion with bounds placed upon the range of performance a user will experience. These bounds are established in the SPS Performance Standard, Section 3, as SPS operational performance standards. This Appendix provides a context in which to view GPS performance standards, through a definition of historical behavior and expected variations for each aspect of system performance. A-1.1 Purpose This Appendix describes documented GPS SPS performance as a function of time to aid the user in comparing historical delivered service to the service levels established in the SPS Performance Standard, Section 3. Although GPS performance has substantially exceeded established service levels, users should place full reliance on the standards of Section 3. This Appendix is to be used for information only. A-1.2 Scope The contents of this Appendix are provided for information purposes only, and do not constitute any commitment on the part of the U.S. Government. Historical performance does not guarantee future behavior. The U.S. Government retains the right to modify constellation management practices as necessary to meet or exceed performance standards. A-1.3 An Overview of SPS Performance Parameters This section provides a description of the basis for defining GPS performance parameters and their associated standards. Background is provided to promote an understanding of the underlying behavior described in succeeding sections. A-1.3.1 Basis for Establishing SPS Performance Standards The performance a GPS user experiences will vary widely due to many factors. With the removal of Selective Availability (SA), these variations have become much more pronounced. The primary factors that drive the performance a GPS user will experience are: • Satellite availability. • Signal-in-Space (SIS) User Range Errors (UREs) for satellites used in the solution, to include single-frequency and C/A code-unique code phase errors. • Constellation geometry. • Receiver design-dependent mask angle (nominal mask angle value, use of a fixed value versus dynamic selection). • Type of solution (for positioning users – a four-satellite solution, a variant of overdetermined solution to include all satellites-in-view, or a solution based on a variant of Receiver Autonomous Integrity Monitoring (RAIM)). Page A-1 October 2001 GPS SPS Performance Standard • Accuracy of United States Naval Observatory (USNO) GPS time offset predictions relative to Coordinated Universal Time (UTC (USNO)), for time transfer users. • The signal propagation environment, to include ionosphere and troposphere delay effects, and scintillation. • The...
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This document was uploaded on 09/26/2013.

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