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How are GPS satellites arranged to provide worldwide coverage?
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Officers on a passenger ship using charts for navigation.
The Global Positioning System (GPS) provides worldwide coverage through a constellation of satellites arranged in six circular orbits around Earth. These satellites are positioned such that they maintain a consistent presence, ensuring that at least four to five satellites are in view from most points on the planet at any given time.12
Key details of this arrangement include:
- Orbital Configuration: The satellites travel in six orbital planes inclined at 55° to the equatorial plane.3
- Altitude and Period: They orbit at an altitude of approximately 12,500 miles (20,000 km) with an orbital period of 12 hours.3
- Constellation Size: While the core constellation consists of two dozen satellites, the system typically includes additional spares in reserve to ensure continuous service.1
By maintaining this specific geometry, the system allows receivers on the ground to calculate precise three-dimensional positions—including longitude, latitude, and altitude—by measuring signal travel times from multiple satellites simultaneously.23