GNSS basics

The Global Navigation Satellite Systems (GNSS) represent a significant advancement in location and navigation technology. This knowledge base provides an overview of the four primary GNSS constellations: GPS, GLONASS, Galileo, and BeiDou. Each system, developed by different global entities, consists of satellites in medium earth orbit (MEO) or geostationary orbit (GEO), offering global or regional coverage. These constellations serve a myriad of applications, from navigation to surveying, and are designed to be interoperable, ensuring enhanced accuracy and reliability. Here, we delve into the unique characteristics, satellite compositions, and functionalities of each system, highlighting their contributions to the field of global positioning and navigation.

Constellations #

(1 + 2 = G2 = PRSRTCM3)

(1 + 2 + 3 + 4 = G4 = PRSRTCM3_G4)

1. GPS (Global Positioning System): Developed by the United States, GPS is the first and most widely used GNSS system. It consists of a constellation of approximately 30 satellites in medium earth orbit (MEO) that transmit signals to GNSS receivers on the ground. GPS provides global coverage and is used for a wide range of applications, including navigation, surveying, and timing.
2. GLONASS (Global Navigation Satellite System): Developed by Russia, GLONASS is a GNSS system that consists of a constellation of approximately 24 satellites in MEO. GLONASS provides global coverage and is designed to be interoperable with GPS. GLONASS is used for navigation, surveying, and other applications.
3. Galileo: Developed by the European Union, Galileo is a GNSS system that consists of a constellation of approximately 30 satellites in MEO and medium earth orbit (MEO). Galileo provides global coverage and is designed to be interoperable with GPS and GLONASS. Galileo is used for navigation, surveying, and other applications.
4. BeiDou: Developed by China, BeiDou is a GNSS system that consists of a constellation of approximately 35 satellites in MEO and geostationary orbit (GEO). BeiDou provides regional coverage and is being expanded to provide global coverage. BeiDou is used for navigation, surveying, and other applications.

Each GNSS constellation provides signals at different frequencies and with different signal characteristics. This allows GNSS receivers to use signals from multiple constellations to improve the accuracy and reliability of position data.