Cycle slip detecting and repairing method based on HHT and support vector machine

Abstract

The invention provides a cycle slip detecting and repairing method based on HHT and a support vector machine. First, an EMD algorithm is used for carrying out multi-time scale decomposition on a code phase second difference time sequence, then IMF components obtained by decomposition are subjected to Hilbert converting; second, according to whether the Hilbert amplitude values of the IMF components change suddenly at the same time, cycle slip is detected; then for the IMF components in which the Hilbert amplitude values change suddenly, support vector machine forecast models are established respectively, the value when cycle slip happens is forecast; finally the forecast value and a practical value are compared, and the magnitude of the cycle slip is determined. The method can be used for cycle slip detecting and repairing of single-frequency or multi-frequency carrier phase observing values, and the sensitivity of cycle slip detecting and the accuracy of cycle slip repairing are improved.

Description

technical field [0001] The invention relates to the technical field of satellite navigation precision positioning, in particular to a cycle slip detection and repair method. Background technique [0002] The principle of satellite navigation and positioning is that when the satellite position is known, the three-dimensional coordinates of the receiver can be calculated by measuring the distance from more than four satellites to the same receiver. Currently, the measurement values ​​used for positioning calculation mainly include pseudo-range measurement values ​​and carrier phase measurement values. Among them, the error of pseudo-range measurement values ​​is large and the positioning accuracy is not high; compared with pseudo-range measurement values, carrier phase measurement values The error is small. When used for positioning, the accuracy of absolute positioning can reach centimeter level, and the relative positioning accuracy can reach millimeter level. Therefore, in...

AI Technical Summary

Problems solved by technology

The high-order difference method can only detect large cycle slips, and it is difficult to repair cycle slips; the ability of polynomial fitting method to detect cycle slips depends on the data sampling interval, and it is difficult to detect small cycle slips; the Doppler frequency shift method requires the receiver to be able to observe Doppler The frequency shift, its ability to measure cycle slip is related to the data sampling interval; the Kalman filter method is only suitable for the case where the carrier is moving at a constant speed and the signal is out of lock for a short time; the code phase quadratic difference method is susceptible to the influence of pseudo-range measurement noise, The detection effect is not ideal

[0006] The second type of method is only applicable to multi-frequency receivers, such as ionospheric residual method, wide-lane combination method, pseudorange / carrier phase combination method, etc.

The ionospheric residual method can detect small cycle slips, but when the dual-frequency carrier phase cycle slips occur at the same time and the ratio of the cycle slip size is close to the frequency ratio, the method fails; the wide-lane combination method has a strong ability to detect cycle slips, but requires a receiver The machine can receive dual-frequency precision P code data, which limits its application; the ability of the pseudorange / carrier phase combination method to detect cycle slips depends on the accuracy of pseudorange measurement, and it is usually difficult to detect small cycle slips

[0007] It can be seen that the above methods have certain limitations, especially for single-frequency receivers, it is generally difficult to detect and repair small cycle slips

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