AA.VI.E.K3FAA-S-ACS-11A · Nov 2023Knowledge
Ground-based and satellite-based navigation systems (orientation, course determination,...
Ground-based and satellite-based navigation systems (orientation, course determination, equipment, tests and regulations, interference, appropriate use of navigation data, signal integrity).
Bottom line
GPS operation is based on the concept of ranging and triangulation from a group of satellites in space that act as precise reference points. The GPS receiver verifies the integrity (usability) of the signals received from the GPS constellation through RAIM to determine if a satellite is providing corrupted information. In situations where the loss of RAIM capability is predicted to occur, the flight must rely on other approved equipment, delay departure, or cancel the flight.
Key numbers
| Number | What it means |
|---|---|
| 5 satellites in view, or 4 satellites plus a barometric altimeter | RAIM minimum |
| Minimum of 4 above the mask angle | GPS satellites |
| Typically less than 100 feet | GPS error |
| Position transmitted no later than 2.0 seconds from measurement | ADS-B latency |
FAA references
- IFH ch. 9 (pp. 9-26–9-27) — FAA-H-8083-15B
- IFH ch. 9 (p. 9-31) — FAA-H-8083-15B
- 14 CFR 91.227 (Automatic Dependent Surveillance-Broadcast (ADS-B) Out equipment performance requirements.) — eCFR current as of 2026-03-05
- 14 CFR 91.171 (VOR equipment check for IFR operations.) — eCFR current as of 2026-03-05
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