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 2017 with one exception. The exception was the report notification requirement for scheduled interruptions. This was met in only 36 of 47 cases (81%)." 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.

PDF icon 2017 GPS SPS Performance Analysis
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UTC Offset Anomaly

On January 25-26, 2016, GPS users experienced a rare anomaly in operations. For several hours, multiple satellites broadcast information regarding the offset between GPS time and UTC in a manner that did not conform to the GPS signal interface specification. Nevertheless, there was no violation of the UTC offset error assertions in the SPS PS for receivers that honor the UTC offset data set fit interval.

Learn more (700 KB PDF)

2017 Performance Metrics

The following data from the report above summarizes the SPS Performance Standard metrics examined for 2017. Document references are linked to corresponding pages in the SPS Performance Standard (1.7 MB PDF). ✔ means "Met."

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Document Section Performance Metric 2017 Status
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 not eval.
3.4.3 SIS URAE Accuracy ≤ 0.002 m/s2 95% Global average at any AOD not eval.
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 not met
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
≥ 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
≥ 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:

Accuracy

Our GPS Accuracy page provides more information about real-world GPS performance. Go there

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