However, GNSS can be used not only for positioning and navigation, but also for precision and accurate timing applications. Some examples of the applications are for airplane and ship navigations. With the global coverage of GPS and other GNSS satellites, position and navigation applications are the main services provided by GPS (and GNSS). The lower the height of the orbit from earth, the higher the number of required satellites to cover the entire earth. For example, GPS has a total of 31 satellites that are active in orbit ( per 16 December 2021). The orbiting speed of the satellites is approximately 3-4 km/s.Īt MEO orbits, GNSS satellites, including GPS, can cover the entire earth surface with only 20-30 satellites. Almost all GNSS constellations are classified as medium-earth-orbit (MEO) satellites and their orbits are between 20000 km to 25000 km above the sea level on earth. GNSS includes GPS (US), GALILEO (EUROPE), GLONASS (RUSSIA), BEIDOU (CHINA), QZSS (JAPAN) and other constellations. GPS is the most well-known and used GNSS constellations since GPS also the first and the pioneer of the GNSS constellation systems. A brief introduction to GPS (GNSS)Īctually, GPS is one of the subsets of satellite constellations called global navigation satellite system (GNSS). But only graphs or plots showing how GPS signals evolve from a satellite to a receiver and from the raw received signals to navigation message demodulation are shown. There will be no mathematical formulas and equations. The introduction is presented in a way that all reader can understand. GPS signals will be used for the explanation of the global navigation satellite system (GNSS) signal processing chain. In this post, gentle explanations focusing on the evolution of GPS signals from a satellite to a receiver and the processing chains from the raw received signals, signal acquisition, tracking to demodulation are presented. The signal of GPS comes from far away in space to a GPS receiver, for example a cell phone or satnav. From their cell phones with GPS assistance technology, they can access maps and find ways. ![]() ![]() Today, almost everybody knows about global positioning system (GPS).
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