③ The GPS satellite signal and the

③ The GPS satellite signal and the differential signal broadcast by the base station must be able to be received simultaneously.The problem of star number limits the application range of GPS RTK technology. GPS RTK measurement will be difficult when the number of stars measured in high-rise buildings and mountain shade areas is less than 5. In the future, when GLONASS satellite is all networked, it will be less difficult to put into production.During the relocation process, it cannot be shut down or locked. It is easy to do not shut down, and it is difficult to lose lock. When the station is moved under trees, under overpasses and tunnels, it may cause lock loss. After the lock is lost, it must be reinitialized, that is, the whole week fuzzy value must be determined again. The time and reliability of the whole week fuzzy value are determined by four factors: single frequency machine or dual frequency machine, number of stars measured, distance from base station, and software quality of gpsrtkrtk.