Which orbit is used for GPS satellites?

• A. LEO
• B. GEO
• C. MEO
• D. HEO

Answer: (C)

GPS satellites operate in medium Earth orbit. This altitude—about 20,200 kilometers above the Earth—gives a practical balance between how many satellites you need for global coverage and how long the signal takes to reach the ground. With several orbital planes and roughly 55-degree inclination, a receiver can typically see multiple satellites at once, which is essential to solve for the receiver’s 3D position and its clock bias using at least four pseudorange measurements.

If you were in a low Earth orbit, you’d need many more satellites to maintain the same visibility as the Earth turns, and the ground geometry wouldn’t be as favorable for stable, global coverage. A geostationary orbit would place satellites fixed over the equator, resulting in poor geometry for users around the globe (and especially near higher latitudes) and larger signal delays, which degrades positioning accuracy. Highly elliptical orbits would produce inconsistent visibility and timing, making reliable navigation impractical. The medium Earth orbit setup is the sweet spot that makes global, precise, and reliable GPS available.