How to locate GPS? The GPS receiver can receive accurate nanosecond time information that can be used for timing; the forecast ephemeris for forecasting the rough position of the satellite in the next few months; the broadcast ephemeris for calculating the satellite coordinates required for positioning , The accuracy is a few meters to tens of meters (different satellites, changing at any time); and GPS system information, such as satellite status. Solar Panel,,High Efficiency Mono Solar Panels,Bifacial Jinko Solar Panels PLIER(Suzhou) Photovoltaic Technology Co., Ltd. , https://www.pliersolar.com
The GPS receiver can measure the code to get the distance from the satellite to the receiver. Because it contains the error of the receiver's satellite clock and the atmospheric propagation error, it is called pseudorange. The pseudo range measured for the 0A code is called the UA code pseudo range, and the accuracy is about 20 meters. The pseudo range measured for the P code is called the P code pseudo range, and the accuracy is about 2 meters.
The GPS receiver decodes the received satellite signal or uses other techniques to remove the information modulated on the carrier, and then the carrier can be restored. Strictly speaking, the carrier phase should be called the carrier beat frequency phase, which is the difference between the received satellite signal carrier phase affected by the Doppler shift and the signal phase generated by the receiver's local oscillation. Generally measured at the epoch time determined by the receiver clock and keeping track of the satellite signal, the phase change value can be recorded, but the initial value of the phase of the receiver and the satellite oscillator at the beginning of the observation is unknown. The phase integer of the initial epoch is also unknown, that is, the ambiguity of the whole week can only be solved as a parameter in data processing. The accuracy of the phase observation value is as high as millimeters, but the premise is to solve the ambiguity of the entire circumference, so the phase observation value can only be used when there is a relative observation and a continuous observation value, and the positioning accuracy that is better than the meter level is only Phase observations can be used.
According to the positioning method, GPS positioning is divided into single-point positioning and relative positioning (differential positioning). Single-point positioning is a way to determine the position of a receiver based on the observation data of a receiver. It can only use pseudorange observations and can be used for rough navigation and positioning of vehicles and ships. Relative positioning (differential positioning) is a method to determine the relative position between observation points based on the observation data of more than two receivers. It can use either pseudorange observations or phase observations. Geodetic or engineering measurements should be used. Use phase observations for relative positioning.
GPS observations include errors such as satellite and receiver clock differences, atmospheric propagation delay, multipath effects, etc., and are also affected by satellite broadcast ephemeris errors during positioning calculations. Most common errors are caused by relative positioning Cancel or weaken, so the positioning accuracy will be greatly improved. The dual-frequency receiver can cancel the main part of the ionospheric error in the atmosphere based on the observations of the two frequencies. When the accuracy requirements are high and the distance between the receivers is long (the atmosphere has a significant difference ), Dual-frequency receivers should be used.
In positioning observation, if the receiver moves relative to the earth's surface, it is called dynamic positioning. For example, it is used for pseudo-range single-point positioning with an accuracy of 30 to 100 meters for rough navigation and positioning of vehicles and ships, or for navigation and positioning of urban vehicles. Pseudorange differential positioning with meter-level accuracy, or centimeter-level phase differential positioning (RTK) for measuring lofts, etc. Real-time differential positioning requires a data link to transmit observation data from two or more stations in real time for calculation. In positioning observation, if the receiver is stationary with respect to the surface of the earth, it is called static positioning. In the observation of the control network, it is generally observed by several receivers at the same time in this way. It can maximize the use of GPS. Positioning accuracy, receivers dedicated to this purpose are called earth-type receivers, and are the best performers among the receivers.
At present, GPS has been able to meet the accuracy requirements of crustal deformation observation, and IGS's perennial observation stations can already form a millimeter-level global coordinate frame.