Satellite navigation systems that let a receiver on the ground work out its precise position and time; GPS is the United States system, while NavIC is India's own regional system.
- A navigation receiver measures the time signals take to arrive from several satellites and uses this to calculate latitude, longitude, altitude, and time (a method called trilateration); at least four satellites are needed for an accurate fix.
- GPS (Global Positioning System) is run by the United States; other global systems include Russia's GLONASS, the European Union's Galileo, and China's BeiDou.
- NavIC (Navigation with Indian Constellation), formally IRNSS, is built by ISRO; it is a regional system covering India and a surrounding region rather than the whole globe.
- NavIC uses a constellation of satellites in geostationary and inclined geosynchronous orbits and provides a standard civilian service and a restricted service for authorised (including military) users.
- Independent navigation matters for sovereignty, since access to foreign systems could be denied during conflict; NavIC is used in services such as vehicle tracking, fishermen alerts, and disaster warnings.
GPS, NavIC/IRNSS, ISRO, and the strategic case for an indigenous navigation system are recurring space and defence-technology items with a direct national-security and self-reliance angle.
NavIC (IRNSS) is regional, covering India and its neighbourhood, not a worldwide system like GPS. GPS is the American system specifically; "GPS" is often used loosely to mean any satellite navigation, but GLONASS, Galileo, BeiDou, and NavIC are separate systems.
Satellite navigation by trilateration: GPS is the United States global system, while NavIC (IRNSS) is ISRO's regional system for India, valued for strategic self-reliance.