🔍 Key Concepts

• Global Positioning System (GPS) constellation design and how many satellites are needed for full global coverage • Minimum number of satellites needed to compute a 3D GPS fix plus timing at a receiver • Difference between minimum required satellites for a position fix and the full operational constellation

💭 Think About

• Think about how many satellites your GPS receiver usually tracks at once and then compare that to how many must be in orbit to cover the entire Earth at all times • Consider that GPS satellites are arranged in several orbital planes; what total number per plane would give reliable worldwide coverage? • Ask yourself which of the choices seems more like a full, planned satellite constellation versus just the bare minimum to get a fix

✅ Before You Answer

• Remember that a basic 3D GPS fix (lat, long, and altitude) plus clock error needs at least 4 satellites in view at your receiver • The GPS constellation must provide global coverage, meaning any point on Earth should see multiple satellites above the horizon at any time • Check which option matches the commonly taught number for the standard GPS constellation used in navigation textbooks and maritime exam prep materials