The main error and elimination algorithm in GPS positioning

　　The main errors in GPS positioning are: star clock errors, relativity errors, earth rotation errors, ionization layers and stream layer errors. 1) Star clock error is formed by the error between the star clock and the GPS standard. The GPS measurement is based on the precision measurement. Clean. Generally use dual -e -terms to indicate the star clock error. (3) In the GPS star calendar, the purpose of the amendment is achieved by sending the coefficient of the dual edition. After this correction, the error between the star clock and the GPS standard can be controlled within 20ns. 2) The theory of relativity is based on the theory of relativity. After the clock with frequency on the ground is installed on a satellite running at a speed, the clock frequency will change.

　　That is, the clock on the satellite is slower than the ground. To correct this error, the method of coefficient improvement can be used. This coefficient is broadcast in the GPS stars to eliminate relativity errors, and the relativity error can be controlled within 70ns. 3) The GPS positioning of the Earth's self -rotation error uses the Agreement Earth coordinate system with the earth solid. Satellite phase is relatively liberalized for the location (coordinate value) of the agreement Earth. If a satellite is at a certain position in the coordinate system of the protocol, the satellite is no longer at the ground signal of the local receiver, and the satellite is no longer at the time of the transmission of the instantaneous position [coordinate value) due to the rotation of the earth. In other words, in order to solve the position of the receiving machine receiving satellite signal in the protocol coordinate system, the coordinate system at this moment must be used as the reference coordinate system for solving. The moment when the satellite position is used to emit signals for satellites. In this way, the satellite position that is solved at that moment must be converted to the position of the reference coordinate system. Let the earth's angle speed to WE, the transmitting signal instantaneous to receiving signal transmission delay is △ T, then the duality adjustment is adjusted to the three -dimensional coordinate adjustment of the three -dimensional coordinate (4) The positioning error caused by the earth rotation in this time is rice. Considering the precision positioning must be considered to be eliminated. 4) Electric ionization layer and convection layer error layer refers to the atmosphere of 50-1000km above the ground above the ground. The gas molecules in the ionization layer have caused a strong ionization due to various ray radiations such as the sun and other celestial bodies, forming a large amount of free electron and positive ions. The ionizing layer error is composed of the ionization layer refraction error and the delayed error of the ionization layer. The error caused by it can reach about 50 meters, and the horizontal direction can reach about 150 meters. At present, a strict mathematical model cannot be used to describe the size and changes of the electronic density. Therefore, the ionization layer correction model or dual -frequency observation is corrected to eliminate the ionization layer error. The stream layer refers to the bottom layer of the atmosphere within about 40km from the ground, accounting for 99%of the entire atmospheric mass. Its atmospheric density is larger than the ionization layer, and the atmospheric state is more complicated. In contact with the ground to get the radiant heat from the ground, the temperature decreases with the height of the height. The refraction of the flow layer includes two parts: one is due to the slowdown of the transmission speed or speed of the electromagnetic waves, which delayed the path in the atmosphere. The second is because the GPS satellite signal also bend The distance is deviated. It can reach 2.5 meters in the vertical direction and the horizontal direction can reach 20 meters. The flow error is also corrected through the experience model. In the GPS star calendar, the ionization layer and the stream layer error are eliminated by the GPS stars and the model parameters. The experimental data show that the effectiveness of the use of the model to the ionization layer error reaches 75%, and the effectiveness of the improvement of the flow layer error is 95%.

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