GNSS satellites can locate terminals on the earth by relying on a three dimensional coordinate system. Satellite positioning has errors. Errors come from both inside and outside the system. For example, errors are caused when
satellite signals penetrate the ionosphere and troposphere, errors caused by the Doppler effect caused by high-speed satellite movement, multipath effect errors, channel errors, satellite clock errors, ephemeris errors, internal noise
errors, and so on. Some of these errors can be completely eliminated, while others cannot be eliminated or can only be partially eliminated, which affects the accuracy and reliability of the system. In order to better eliminate errors
and improve positioning accuracy, industry experts have developed a more powerful positioning technology, which is RTK, which reduces the error unit from meters to centimeters.