Official U.S. Government information about the
Global Positioning System (GPS) and related topics
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, confirms that, "in 2013 all of the SPS PS assertions examined were met or exceeded." The assertions evaluated include those associated with the accuracy, integrity, continuity, and availability of the GPS signal-in-space and the position performance standards.
2013 GPS SPS Performance AnalysisDownload 2.4 MB
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. Learn more (700 KB PDF)
2013 Performance Metrics
The following data from the report above summarizes the SPS Performance Standard metrics examined for 2013. Document references are linked to corresponding pages in the SPS Performance Standard (1.7 MB PDF). ✔✚ means "Met or Exceeded."
| Document Section | Performance Metric | 2013 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 | ✔✚ | |
| 3.5.1 SIS Instantaneous URE 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 | ✔✚ |
| 3.7.1 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 con guration 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 |
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:
- Real-time plots of GPS SPS Position Dilution of Precision (PDOP)
- Monthly GPS Report Cards
- Quarterly GPS Performance Analysis Reports
- And more
Accuracy
Our GPS Accuracy page provides more information about real-world GPS performance. Go there
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