Global Positioning Systems (GPS) and Natural Hazards

Synonyms

Global Satellite Positioning System; GPS; Sat Nav

Definition

Global Positioning Systems (GPS) are all-weather systems based on constellations of satellites that allow worldwide terrestrial, maritime, and aerial navigation and position determination, using passive receivers that triangulate a three-dimensional position based on radio signals received from at least four satellites.

Discussion

Although Global Positioning System (GPS) is a generic term, it has become synonymous with the US-operated NAVSTAR GPS. With the first satellites launched in 1978, it became fully operational in 1995. Developed primarily for military purposes, it remains the only complete global satellite-based positioning system. It employs 24 active satellites orbiting at approximately 20,200 km altitude, ensuring that between 4 and 12 satellites are within direct line of sight of anywhere on Earth. Three-dimensional positions are determined using passive devices that receive encoded signals from at least...