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the U.S. Department of Defense (DoD) to discontinue the use of SA effective midnight May 1,
2000. This edition of the SPS Performance Standard establishes new performance standards
that reflect the removal of SA. 1.1 Purpose The SPS Performance Standard defines levels of performance the U.S. Government commits to
provide to civil GPS users. This document is written to satisfy the following objectives:
1) Identify performance standards the U.S. Government uses to manage SPS performance.
2) Standardize SPS performance parameter definitions and assessment methodologies.
3) Describe historical SPS performance characteristics and ranges of behavior.
Appendix A to this document provides information to the civil community concerning historical
performance, ranges of performance possible under varying operational conditions, and
operational characteristics of the GPS constellation. Appendix A is provided for informational
Appendix B to this document provides a list of key terms and definitions, and acronyms used in
the SPS Performance Standard. 1.2 Scope The SPS Performance Standard is published by the Office of the Secretary of Defense, in
accordance with the Memorandum of Agreement (MOA) between the DoD and the Department of
Transportation (DOT) regarding civil use of the Global Positioning System (Section 5, Paragraph
In keeping with the purpose defined in the DoD/DOT MOA, this document defines standards for
SPS Signal-in-Space (SIS) performance. SPS performance standards are independent of how
the user applies the basic positioning and timing services provided. These performance
standards are based on signal-in-space performance. Contributions of ionosphere, troposphere,
receiver, multipath, or interference are not included.
This SPS Performance Standard establishes new definitions and relationships between
traditional performance parameters such as service availability, service reliability, and accuracy.
GPS performance specifications have previously been made to conform to definitions that apply
Page 1 October 2001 GPS SPS Performance Standard to fixed terrestrial positioning systems. The new definitions are tailored to better represent the
performance attributes of a space-based positioning and time transfer system. 1.3 The GPS Standard Positioning Service The GPS SPS is a positioning and timing service provided on the GPS L1 signal. The L1 signal,
transmitted by all GPS satellites, contains a Coarse/Acquisition (C/A) code and a navigation data
message. The GPS L1 signal also contains a Precision P(Y) code that is reserved for military use
and is not a part of the SPS.
The L-band SPS ranging signal is a 2.046 MHz null-to-null bandwidth signal centered about L1.
The transmitted ranging signal that comprises the GPS-SPS is not limited to the null-to-null signal
and extends through the band 1563.42 to 1587.42 MHz.
GPS satellites also transmit a second ranging signal known as L2. The L2 signal is not part of the
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