What is the reference coordinate system used by the Global Positioning System (GPS)?

The Global Positioning System (GPS) uses the World Geodetic System 1984, commonly known as WGS 84, as its reference coordinate system. WGS 84 is a global reference frame that defines precise locations on the Earth's surface, allowing GPS devices to provide accurate positioning information.

This system is crucial because it integrates various geodetic parameters, including a specific ellipsoid shape that approximates the Earth's shape and gravitational variations, as well as referencing a consistent coordinate system. Using WGS 84, GPS can determine a position by triangulating signals from multiple satellites, which continuously transmit their locations and the precise time.

The other choices represent different geodetic systems or datums that serve in specific contexts but are not used by GPS for global positioning. A vertical datum like NAVD88 (North American Vertical Datum of 1988) pertains to elevation and height measurements in North America, while the International Terrestrial Reference System focuses on the Earth’s solid surface rather than providing the specific global positioning required by GPS. Therefore, WGS 84 stands out as the fundamental reference system for GPS operations worldwide.