GPS Performance

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Accuracy

The U.S. government is committed to providing GPS to the civilian community at the performance levels specified in the GPS Standard Positioning Service (SPS) Performance Standard (PS). View document

The following study, commissioned by the Space Force, concludes that, "All the SPS PS assertions examined in this report were met in 2022." The assertions evaluated include those of accuracy, integrity, continuity, and availability of the GPS signal-in-space (SIS) along with the assertions on accuracy of positioning and time transfer.

2022 GPS SPS Performance Analysis
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2022 Performance Metrics

The following data from the report above summarizes the SPS Performance Standard metrics examined for 2022. Document references are linked to corresponding pages in the 2020 SPS Performance Standard (2.1 MB PDF).

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Document Section	Performance Metric	Signal Status			System Status
Document Section	Performance Metric	L1 C/A	L1 C/A + L2C	L1 C/A + L5Q	System Status
3.3.1 SIS Per-Satellite Coverage	100% Coverage of Terrestrial Service Volume	−	−	−	NE
3.3.2 SIS Constellation Coverage	100% Coverage of Terrestrial Service Volume	−	−	−	✔
3.4.1 SIS URE Accuracy	≤ 7.0 m 95% Global Statistic URE during normal operations over all AODs	✔	✔	✔	−
	≤ 9.7 m 95% Global Statistic URE during normal operations at any AOD	✔	✔	✔	−
	≤ 3.8 m 95% Global Statistic URE during normal operations at zero AOD	✔	✔	✔	−
	≤ 30 m 99.94% Global Statistic URE during normal operations	✔	✔	✔	−
	≤ 30 m 99.79% Worst case single point Statistic URE during normal operations	✔	✔	✔	−
	≤ 388 m 95% Global Statistic URE during extended operations after 14 days without upload	NE	−	−	−
	≤ 2.0 m 95% Global Statistic URE during normal operations over all AODs for the ensemble of constellation slots	✔	✔	✔	−
3.4.2 SIS URRE Accuracy	≤ 0.006 m/s 95% Global Statistic URRE during normal operations at any AOD	✔	✔	✔	−
3.4.3 SIS URAE Accuracy	≤ 0.002 m/s² 95% Global Statistic URAE during normal operations at any AOD	✔	✔	✔	−
3.4.4 SIS UTCOE Accuracy	≤ 30 nsec 95% Global Statistic UTCOE during normal operations at any AOD	✔	✔	✔	−
3.5.1 SIS Instantaneous URE Integrity	≤ 1×10⁻⁵ Probability over any hour of exceeding the NTE tolerance without a timely alert	✔	✔	✔	−
3.5.4 SIS Instantaneous UTCOE Integrity	≤ 1×10⁻⁵ Probability over any hour of exceeding the NTE tolerance without a timely alert during normal operations	✔	✔	✔	−
3.5.5 SIS Instantaneous P_sat and P_const	≤ 1×10⁻⁵ Fraction of Time When the SPS SIS Instantaneous URE Exceeds the NTE Tolerance Without a Timely Alert (P_sat)	✔	✔	✔	−
3.5.5 SIS Instantaneous P_sat and P_const	≤ 1×10⁻⁸ Fraction of Time When the SPS SIS Instantaneous URE from Two or More Satellites Exceeds the NTE Tolerance Due to a Common Cause Without a Timely Alert (P_const)	✔	✔	✔	−
3.6.1 SIS Continuity - Unscheduled Failure Interruptions	≥ 0.9998 Probability over any hour of not losing the SPS SIS availability from the slot due to unscheduled interruption	✔	−	−	−
3.6.3 Status and Problem Reporting	Appropriate NANU issued at least 48 hours prior to a scheduled event for 95% of the events	✔	✔	✔	−
3.7.1 SIS Per-Slot Availability	≥ 0.957 Probability that (a.) a slot in the baseline 24-slot will be occupied by a satellite broadcasting a healthy SF C/A-Code SPS SIS, or (b.) a slot in the expanded configuration will be occupied by a pair of satellites each broadcasting a healthy SF C/A-Code SPS SIS	✔	−	−	−
3.7.2 SIS Constellation Availability	≥ 0.98 Probability that at least 21 slots out of the 24 slots will be occupied by a satellite (or pair of satellites for expanded slots) broadcasting a healthy SF C/A-Code SPS SIS	✔	−	−	−
3.7.2 SIS Constellation Availability	≥ 0.99999 Probability that at least 20 slots out of the 24 slots will be occupied by a satellite (or pair of satellites for expanded slots) broadcasting a healthy SF C/A-Code SPS SIS	✔	−	−	−
3.7.3 Operational Satellite Counts	≥ 0:95 Probability that the constellation will have at least 24 operational satel- lites regardless of whether those operational satellites are located in slots or not	−	−	−	✔
3.8.1 PDOP Availability	≥ 98% Global PDOP of 6 or less	✔	−	−	−
3.8.1 PDOP Availability	≥ 88% Worst site PDOP of 6 or less	✔	−	−	−
3.8.2 Position Service Availability	≥ 99% Horizontal Service Availability, average location	✔	−	−	−
	≥ 99% Vertical Service Availability, average location	✔	−	−	−
	≥ 90% Horizontal Service Availability, worst-case location	✔	−	−	−
	≥ 90% Vertical Service Availability, worst-case location	✔	−	−	−
3.8.3 Position/Velocity/Time Service Accuracy	≤ 8 m 95% Horizontal error, global average	✔	−	−	−
	≤ 13 m 95% Vertical error, global average	✔	−	−	−
	≤ 15 m 95% Horizontal error, worst site	✔	−	−	−
	≤ 33 m 95% Vertical error, worst site	✔	−	−	−
	≤ 0.2 m/s 95% Velocity error, any axis	✔	−	−	−
	≤ 30 nsec Time Transfer error 95% of the time	✔	−	−	−

✔ means "Assertion met"
✗ means "Assertion not met"
"NE" means "Assertion not evaluated"
− means "No assertion"
Column with results for L1 C/A + L5Q is shown in grey, as L5 is pre-operational and set unhealthy. Results for this column show L1 C/A + L5Q metrics using only the L1 C/A health status.

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Previous Year Performance Reports

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FAA Data

The Federal Aviation Administration publishes additional data on GPS performance as monitored by the ground reference network of the Wide Area Augmentation System (WAAS). The data include:

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