GPS satellites are actually positioned in what is known as medium Earth orbit (MEO) for several reasons:
Coverage: MEO allows for a good compromise between coverage and signal strength. Satellites in MEO can provide global coverage, as they orbit at an altitude of approximately 20,200 kilometers (12,550 miles). This ensures that there are enough satellites distributed around the Earth to maintain consistent and reliable positioning signals.
Signal quality: By operating in MEO, GPS satellites are able to provide better signal quality compared to satellites in higher orbits. The signals transmitted from MEO satellites are less susceptible to atmospheric interference, such as signal degradation due to the ionosphere and troposphere.
Orbital stability: MEO provides a relatively stable orbit for satellites, allowing them to maintain consistent positions in the sky relative to Earth's surface. This stability is important for accurately calculating and predicting satellite positions, which is necessary for precise GPS positioning.
Latency: Satellites in MEO provide lower latency than those in higher orbits, such as geostationary orbit. Lower latency means that the time delay between sending a signal from a GPS receiver and receiving a response from a satellite is minimized, resulting in faster and more responsive positioning data.
Overall, the choice of MEO for GPS satellites strikes a balance between global coverage, signal quality, orbital stability, and latency, ensuring the effective functioning of the GPS system for navigation and positioning purposes.