Operations nominal 24 satellite constellation as of

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Unformatted text preview: 11-31 4-11 11-25 11-20 4-20 4-24 0 9-11 95% Vertical Error Worst Site 3-31 95% Vertical Error (meters) 25 GPS Satellite PRN Combination Removed Figure A-5-4. Worst-Case Vertical Performance with Two SVs Out, Current Ops URE Accuracy degrades considerably under the combination of worst-case satellite outages and worst-case URE performance, as shown in Figure A-5-5 and Figure A-5-6. Even under these conditions, all but one of the 276 two-satellite out cases supported the worst-case site horizontal accuracy standard, and all two-satellite out cases supported the vertical standard. Ensuring the accuracy standards are met when the system is operating at the outer edges of its operational limit will require close monitoring and management of system performance in the event the conditions that lead to worst-case performance are expected to occur. Page A-27 October 2001 GPS SPS Performance Standard Worst 20 Cases of Two Satellites Out -- Horizontal 95% Error Worst Case URE Performance 95% Horizontal Error (meters) 50 45 Worst Site Horizontal 95% Accuracy 40 Global Horizontal 95% Accuracy ANALYSIS CONDITIONS - Current Operations Nominal 24 Satellite Constellation (as of 19 June 2000) 35 30 - 5 x 5 degree global grid spacing with one minute sample steps over 24 hours 25 20 - All-in-view position solution with five degree mask angle 15 10 - 6 meter constellation RMS User Range Error (URE) 5 22-31 11-29 4-7 1-20 21-29 3-31 1-25 2-26 3-22 2-10 10-26 7-20 7-26 2-20 11-31 2-11 2-27 7-11 22-25 11-25 0 GPS Satellite PRNs Removed Figure A-5-5. Worst-Case Horizontal Performance with Two SVs Out, Worst-Case URE Worst 20 Cases of Two Satellites Out -- Vertical 95% Error Worst Case URE Performance 95% Vertical Error (meters) 80 ANALYSIS CONDITIONS Worst Site Vertical 95% Accuracy 70 Global Vertical 95% Accuracy 60 - Current Operations Nominal 24 Satellite Constellation (as of 19 June 2000) 50 - 5 x 5 degree global grid spacing with one minute sample steps over 24 hours 40 30 - All-in-view position solution with five degree mask angle 20 - 6 meter constellation RMS User Range Error (URE) 10 3-22 10-26 11-29 2-10 22-31 22-25 1-25 2-26 4-7 2-11 7-20 2-27 3-31 21-29 1-20 7-26 2-20 7-11 11-31 11-25 0 GPS Satellite PRNs Removed Figure A-5-6. Worst-Case Vertical Performance with Two SVs Out, Worst-Case URE A-5.3 Representative SPS SIS Position Accuracy Characteristics As seen in Figure A-2-3, the GPS constellation has historically enjoyed an overage of satellites above the core 24-satellite constellation number. This trend is illustrated best by viewing performance as seen over a representative month. Such a month of performance (June 2000) is shown in Figure A-5-7 and Figure A-5-8. As can be seen, both global average and worst-case site performance is generally very consistent. Page A-28 October 2001 GPS SPS Performance Standard GPS SPS Global Horizontal Performance -- June 2000 6 95% Horizontal Error (meters) ANALYSIS CONDITIONS 5 - Analysis conducted under normal constellation opera...
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This document was uploaded on 09/26/2013.

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