Which orbit is commonly used for navigation systems such as GPS?

• A. Medium Earth Orbit (MEO)
• B. Low Earth Orbit (LEO)
• C. Geostationary Orbit (GEO)
• D. Highly Elliptical Orbit (HEO)

Answer: (A)

Medium Earth Orbit provides a practical balance for navigation systems: it sits high enough to give a wide view of the sky so receivers can see multiple satellites at all times, but not so far that signals become weak or timing delays blow up. GPS satellites are placed in a roughly 20,200 km altitude with about a 12-hour orbit, arranged in several planes to yield good geometric coverage globally. This setup means a receiver can usually lock onto enough satellites simultaneously to compute a precise position and accurate time, no matter where you are on Earth.

Geostationary orbits stay fixed above one spot on the equator, which limits coverage for high latitudes and means you’d need many GEOs spread out to avoid poor geometry; the distances are also large, which affects signal strength and timing precision. Low Earth orbits are closer and produce strong signals, but maintaining continuous global coverage would require a much larger, more complex constellation and frequent handoffs as satellites zip across the sky. Highly Elliptical Orbits vary widely in distance and elevation angle, causing inconsistent geometry and timing, which is unsuitable for a stable navigation solution.

So the moderate, evenly distributed MEO constellation gives reliable, global coverage with manageable satellite numbers and stable geometry, making it the best fit for navigation systems like GPS.