The GPS receiver can receive the time information that can be used to be used for time -to -nano -seconds; it is used to predict the forecast star calendar in the future of satellites in the next few months; , The accuracy is several meters to tens of meters (different satellites are different, change at any time); and GPS system information, such as satellite conditions.

　　The measurement of the GPS receiver can get the distance from the satellite to the receiver. Because the error containing the receiver satellite clock and the atmospheric dissemination error, it is called a pseudo -distance. The pseudo -tagging distance from 0A is called UA code pseudo -pseudo -pseudo -pseudo -pseudo -pseudo -pseudo -precision is about 20 meters. The pseudo -pseudo distance from P code is called p code pseudo distance, and the accuracy is about 2 meters.

　　The GPS receiving machine decodes or uses other technologies for the receiving satellite signals. After removing the information on the carrier, the carrier can be restored. Strictly speaking, the carrier phase should be called the carrier frequency phase. It is the difference between the signal phase of the satellite signal carrier of the Doppler frequency transparent and the receiving machine. Generally, the number of times of calendar time determined by the receiver clock and maintaining the tracking of satellite signals can record the change value of the phase, but the initial value of the receiver and the satellite oscillator when you start observation is unknown. The phase integer of the original element is also unknown, that is, the fuzzyness of the week, and can only be used as a parameter in data processing. The accuracy of the phase observation value is as high as millimeter, but the premise is to solve the fuzzyness of the entire week. Therefore, the phase observation value can be used only when the relative positioning and a continuous observation value can be used. Can use phase observation values.

　　According to the positioning method, GPS positioning is divided into single -point positioning and relative positioning (differential positioning). The single -point positioning is to determine the position of the receiving machine based on the observation data of a receiver. It can only use a pseudo -distance observation capacity, which can be used for rough navigation positioning of vehicles and boats. Relative positioning (differential positioning) is the method of determining the relative position between the observation points based on the observation data of the receiver of the two or more. Use phase observation values for relative positioning.

　　In the GPS observation volume, the bell difference, atmospheric transmission, and multi -path effects of satellite and receiving machines are included in the GPS observation measurement. When the positioning is calculated, the satellite broadcasting star calendar error should be affected. Cancel off or weakening, so the positioning accuracy will be greatly improved. The dual -frequency receiver can offset the main part of the ionization error of the atmosphere in the atmosphere according to the observation of the two frequencies. ), A dual -frequency receiver should be selected.

　　When the positioning observation, if the receiver is moved by the surface of the earth, it is called dynamic positioning. If the accuracy of a rough navigation positioning for vehicles and boats is a pseudo -distance single -point positioning of 30 to 100 meters, or for urban vehicle navigation positioning The pseudo -distance differential positioning of the rice -level accuracy, or the centimeter -level phase differential positioning (RTK) used to measure the sample, and calculate the observation data of two or more stations in real time. When the positioning observation, if the receiver is static relative to the surface of the earth, it is called a static positioning. When the control network observation is performed, this method is generally observed by several receivers at the same time. Positioning accuracy, which is dedicated to this purpose, is called a earth -type receiver, and is the best performance in the receiver. At present, GPS has been able to meet the accuracy requirements of crustal transformation observation. IGS's perennial observation platform has a global coordinate framework that can form a millimeter level.

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