← Standards & Specs
The Toolbox — Standards
GPS & Satellite
GPS constellation specifications, accuracy standards, HDOP reference, and satellite navigation frequencies.
| Specification | Value / Notes |
|---|---|
| GPS constellation | Minimum 24 operational satellites, 6 orbital planes |
| GPS orbital altitude | 20,200 km |
| GPS orbital period | 12 hours (2 orbits per day) |
| GPS L1 frequency | 1575.42 MHz |
| GPS L2 frequency | 1227.60 MHz |
| GPS L5 frequency | 1176.45 MHz |
| Minimum satellites for 2D fix | 3 satellites |
| Minimum satellites for 3D fix | 4 satellites |
| Standalone GPS accuracy (post-SA) | Approximately 3–5 meters CEP |
| DGPS accuracy | 1–3 meters |
| HDOP — ideal | Less than 2 |
| HDOP — acceptable | 2–5 |
| HDOP — poor | Greater than 6 |
| NMEA 0183 default baud rate | 4800 baud |
| NMEA 2000 data rate | 250 kbps |
| INMARSAT geostationary altitude | 35,786 km |
| INMARSAT coverage limit | Approximately 76°N to 76°S latitude |
| GLONASS L1 frequency | 1602.000 MHz |
| Galileo E1 frequency | 1575.420 MHz (shares GPS L1) |
| BeiDou B1 frequency | 1561.098 MHz |
| COSPAS-SARSAT detection frequency | 406.028 MHz |
| COSPAS-SARSAT homing frequency | 121.500 MHz |
| AIS Channel 1 | 161.975 MHz (Ch 87B) |
| AIS Channel 2 | 162.025 MHz (Ch 88B) |