How does GPS satellite geometry contribute to global coverage?

• A. By using a single satellite to triangulate position
• B. By aligning with ground beacons
• C. Orbital planes; they ensure there are always 5 satellites in view at all times from all areas on the surface
• D. Through satellite radio link with air traffic control

Answer: (C)

The main idea is that GPS achieves global coverage through the way satellites are arranged in multiple orbital planes around the Earth. This distribution keeps satellites spread out rather than clustered in one path, so as the satellites move and the Earth rotates, there are always several visible from any point on the surface. With signals from at least four satellites, a receiver can determine the three spatial dimensions and the receiver’s clock error; having more satellites in view improves the geometry, increasing accuracy and reliability. In practice, this arrangement tends to give you about five or more satellites in view most of the time, which helps ensure a solid fix even if some satellites are temporarily blocked. Other concepts, like relying on a single satellite, using ground beacons, or a satellite link with air traffic control, don’t describe how GPS provides position and timing.