1. Pseudo -distance measurement and pseudo -distance single -point positioning

　　The pseudo -distance measurement is to determine the distance from the satellite to the receiver, that is, the metering code signal transmitted by the satellite to reach the GPS receiver is multiplied by the speed of light. The single point positioning of the pseudo-distance method is to use the GPS receiver to determine the pseudo-distance distance with more than 4 GPS satellites at a moment, and the instantaneous instantaneous coordinates of satellite obtained from satellite navigation. 3D coordinates in the coordinate system.

　　2. Carrier phase measurement and carrier phase positioning

　　The carrier phase measurement is the phase delay from the GPS satellite carrier signal to the receiver antenna. The GPS satellite carriers are preserved on the ranging code and navigation electrical text. After receiving the satellite signal, the ranging code and satellite electrical text on the carrier are first removed, and the carrier is re -obtained. It is called rebuilding the carriers. The GPS receiver will obtain the phase difference between the satellite reconstruction carrier and the vibration signal generated by the receiver through the phase meter by the phase meter.

　　3. Real -time differential positioning

　　The principle of real -time differential positioning of GPS is to place the GPS receiver (referred to as the benchmark station) on the existing accurate heart coordinate points, and use the known ground -hearted coordinates and the Star Calendar to calculate the correction value of the GPS observation value, and use radio communication through radio communication Equipment (referred to as a data chain) sends the correction to the GPS receiver (called a mobile station) in the movement. The liquid station uses the correctional value to modify its own GPS observation value to eliminate the above errors, thereby improving real -time positioning accuracy. There are many types of GPS dynamic differential methods, including location differences, pseudo -distance differences (RTD), carrier phase real -time difference (RTK), and wide -area differences

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