Global Navigation Satellite System in Precision Agriculture
Global Navigation Satellite System Operation
There are three main components of any GNSS: satellite component, control segment, and user segment. The satellite segment describes the GNSS constellations orbiting between 20,000 and 37,000 kilometers above the Earth. These satellites broadcast signals that identify which satellite is transmitting and its time, orbit, and status or health. The second component of any GNSS is a control segment. The control segment is a network of master control, data uploading, and monitoring stations located around the world. These stations receive a satellite’s signal and compare where the satellite says it is with orbit models showing where it should be. Operators at these stations can control the satellite’s position to correct or alter their orbital path, for example, if a satellite has drifted or needs to be moved to avoid debris collision. This process and monitoring of a satellite’s health ensure a baseline of accuracy in GNSS positioning.
Types of Global Navigation Satellite Systems
A GNSS (Global Navigation Satellite System) is a general term for any satellite constellation providing positioning, navigation, and timing (PNT) data. The four main GNSS constellations are GPS (US), GLONASS (Russia), Galileo (EU), and BeiDou (China). Additionally, regional constellations like QZSS (Japan) and IRNSS (India) are worth noting. These systems transmit their signals using radio frequencies in the L-Band, but each constellation might use different frequencies or label them differently (Table 5.1). Together, these constellations are called the Global Navigation Satellite System (GNSS). Important to note there are satellite-based augmentation systems (SBAS), which provide global error corrections for improved accuracy in GNSS applications. Many countries manage their own SBAS systems, and these are usually considered separate from traditional GNSS constellations..
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