1. Briefly describe the basic principles of GPS carrier phase measurement.
Carrier phase measurement is a technique that uses a receiver to determine the carrier phase observations or their differential observations, and then resolves with the baseline vector to obtain the baseline vector coordinate difference between two synchronized observation stations.和 方法。 And methods. The difference between the phase of the reference signal generated by the receiver in a specified epoch and the phase of the satellite carrier signal received at this time (also known as the instantaneous carrier phase difference), this value is measured by station, satellite, observation epoch 3 The indirect observations (called the carrier phase difference observations) obtained by performing differential processing on each element. According to the number of differences, it can be divided into primary difference, secondary difference and tertiary difference observations. These two observations contain the distance information from the satellite to the receiver, and it and the time change of the satellite distance are both a function of the position of the satellite and the receiver, so they can be used for receiver positioning and satellite orbit determination.
If a satellite S sends out a carrier signal, at a certain moment, the phase of the signal at the receiver R is medium R, and the phase at the satellite S is medium S. The satellite ground distance is: ρ = λ (medium S-φR), where (medium S-medium R) is the phase difference. The carrier phase observation value at a certain moment refers to the difference between the phase R of the reference signal generated by the receiver at that moment and the phase φR of the received carrier from the satellite (φR-qR). Based on this, the exact distance between the satellite receivers p = λ (medium S-medium R) = λ (medium R-φR) is obtained.
2. In high-precision GPS measurement, why do we need to use carrier phase measurement method for three-dimensional positioning.
Carrier phase observations must be used for high-precision GPS measurement. RTK positioning technology is a real-time dynamic positioning technology based on carrier phase observations. It can provide real-time 3D positioning results of the measurement station in a specified coordinate system and achieve centimeter-level accuracy. In RTK operation mode, the base station transmits its observation value and station coordinate information to the rover through the data link. The rover not only receives the data from the reference station through the data link, but also collects the GPS observation data, and composes the differential observation value in the system for real-time processing, and at the same time gives the centimeter-level positioning result, which takes less than one second. The rover can be in a static state or in a moving state; it can be initialized at a fixed point before entering a dynamic operation, or it can be directly turned on under dynamic conditions, and the search and solution of the ambiguity of the entire cycle can be completed in a dynamic environment. After the unknowns are fixed for a whole week, each epoch can be processed in real time. As long as the tracking of the phase observations of more than four satellites and the necessary geometry can be maintained, the rover can always give centimeter-level positioning results.
3. In the carrier phase measurement, what are the main methods to determine the unknown number of the whole week?
1. Use pseudorange straightness to determine
2. Use more accurate satellite ephemeris and prior station coordinates to determine
3. Determine by adjustment calculation
