GPS Performance

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 Air Force, concludes that, "All the SPS PS assertions examined in the report were met in 2019." 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.

2019 GPS SPS Performance Analysis
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2019 Performance Metrics

The following data from the report above summarizes the SPS Performance Standard metrics examined for 2019. Document references are linked to corresponding pages in the 2008 SPS Performance Standard (1.7 MB PDF). ✔ means "Met."

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Document Section	Performance Metric	2019 Status
3.3.1 SIS Per-Satellite Coverage	100% Coverage of Terrestrial Service Volume	not eval.
3.3.2 SIS Constellation Coverage	100% Coverage of Terrestrial Service Volume	✔
3.4.1 SIS URE Accuracy	≤ 7.8 m 95% Global average URE during normal operations over all AODs	✔
	≤ 6.0 m 95% Global average URE during normal operations at zero AOD	✔
	≤ 12.8 m 95% Global average URE during normal operations at any AOD	✔
	≤ 30 m 99.94% Global average URE during normal operations	✔
	≤ 30 m 99.79% Worst case single point average URE during normal operations	✔
	≤ 388 m 95% Global average URE after 14 days without upload	N/A
3.4.2 SIS URRE Accuracy	≤ 0.006 m/s 95% Global average at any AOD	✔
3.4.3 SIS URAE Accuracy	≤ 0.002 m/s² 95% Global average at any AOD	✔
3.4.4 SIS UTCOE Accuracy	≤ 40 nsec 95% Global average 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	✔
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 Problems Reporting	Appropriate NANU issued at least 48 hours prior to a scheduled event	✔
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 SPS SIS, or (b.) a slot in the expanded configuration will be occupied by a pair of satellites each broadcasting a healthy 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 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 SIS	✔
3.7.3 Operational Satellite Counts	≥ 0.95 Probability that the constellation will have at least 24 operational satellites 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, average location	✔
	≥ 99% Vertical, average location
	≥ 90% Horizontal, worst-case location
	≥ 90% Vertical, worst-case location
3.8.3 Position Accuracy	≤ 9 m 95% Horizontal, global average	✔
	≤ 15 m 95% Vertical, global average
	≤ 17 m 95% Horizontal, worst site
	≤ 37 m 95% Vertical, worst site
	≤ 40 nsec time transfer error 95% of the time	✔

Previous Year Performance Reports

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: