What is the principle of GPS positioning?

◆Positioning principle
GPS positioning includes pseudo-range single point positioning, carrier phase positioning and real-time differential positioning.
1. Pseudo-range measurement and pseudo-range single-point positioning
Pseudo-range measurement is to measure the distance from the satellite to the receiver, that is, the distance obtained by multiplying the propagation time of the ranging code signal transmitted by the satellite to the GPS receiver multiplied by the speed of light. Pseudo-law bill
Point positioning is to use the GPS receiver to measure the pseudo-range with more than 4 GPS satellites at a certain moment, and the satellite instantaneous coordinates obtained from the satellite navigation message, using the distance

The intersection method is used to obtain the three-dimensional coordinates of the antenna in the WGS-84 coordinate system.

2. Carrier phase measurement and carrier phase positioning
Carrier phase measurement is the determination of the phase delay between the GPS satellite carrier signal and the receiver antenna. The ranging code and navigation message are modulated on the GPS satellite carrier, and the receiver receives
After receiving the satellite signal, the ranging code and satellite message on the carrier are removed first, and the carrier is re-obtained, which is called rebuilding the carrier. The GPS receiver reconstructs the carrier wave from the satellite and the oscillator in the receiver

The local oscillator signal generated by the oscillator is compared with the phase by the phase meter, and the phase difference can be obtained.

3. Real-time differential positioning
The principle of GPS real-time differential positioning is to place a GPS receiver (called a reference station) on an existing precise geocentric coordinate point, and use the known geocentric coordinates and ephemeris to calculate the GPS viewpoint.
The correction value of the measured value is sent to the GPS receiver in motion (called the rover) through the radio communication equipment (called the data link). Rover Utilizes Calibration ValuesCorrect your own GPS observations to eliminate the above errors, thereby improving real-time positioning accuracy. There are many methods of GPS dynamic difference, mainly position difference, pseudo-range differencepoints (RTD), carrier phase real-time differential (RTK) and wide-area differential, etc.

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