GNSS (or Global Navigation Satellite System) is a broad term encompassing different types of satellite-based positioning, navigation and timing (PNT) systems used globally. GPS (or Global Positioning System) is one such type of Global Navigation Satellite System.
Originally known as “NAVSTAR” (Navigation Satellite Timing and Ranging), GPS was developed by the US Department of Defense for military use back in the 1970s. After the first satellite launch in 1978 technology utilizing GPS evolved quickly, and it began to infiltrate various aspects of our daily lives. However, it wasn’t until after 2000 that it became truly ubiquitous – following the switching-off of Selective Availability. For more information about Selective Availability please see our blog on its conception, lifetime, and abrupt end:
GNSS use constellations of satellites and are based on the. Put simply, this means that GNSS receivers accurately determine their own location by measuring the distance to four or more satellites. Initially these satellites would all have been from one GNSS, but multi-GNSS receivers are now commonplace.
For a long time, GPS and itswere the only available GNSS. As the more reliable of the two systems through this period – GLONASS went through a long period of disrepair – GPS became the most widely used GNSS, and that remains the case to this day.
However, with the regeneration of GLONASS, and the advent of Europe’s Galileo system and China’s BeiDou, users and developers are now presented with a broader range of signals and all the benefits that this brings with it. In addition to these global systems, there are a number of regional and wide area augmentation systems – but these are a subject for another time.