Self-adjustment Kalman filtering-based pseudo-range smoothing method by using Doppler frequency shift and carrier phase

Abstract

The invention discloses a self-adjustment Kalman filtering-based pseudo-range smoothing method by using Doppler frequency shift and carrier phase and belongs to the global satellite navigation system pseudo-range single-point positioning field. According to the method of the invention, the Doppler frequency shift is utilized to estimate the initial value of a code pseudorange; cycle slip detection is completed based on the carrier phase, and therefore, the smoothing mode of a Kalman filter and the variance of process noises can be determined; the self-adjustment of the observation noise variance of the Kalman filter is realized through using the change condition of the measured value of a signal to noise ratio; and finally, the smoothing of the code pseudo-range is completed. With the method adopted, the problem of low precision of the code pseudo-range is solved, influence on pseudo-range smoothing of the carrier phase caused by cycle slip is eliminated, high-precision pseudo-ranges can be obtained under a complex environment, and therefore, the accuracy of single-point positioning can be improved. The method is not restricted to static positioning conditions and has a bright broad application prospect.

Description

technical field [0001] The invention relates to the field of pseudo-range single-point positioning of a global satellite navigation system, in particular to a Doppler-assisted carrier phase smoothing pseudo-range method based on self-adjusting Kalman filtering. Background technique [0002] The code pseudorange, carrier phase and Doppler frequency shift observations can be obtained from the baseband signal of the Global Navigation Satellite System (GNSS) receiver. Code pseudo-range has been regarded as the most important basic distance measurement value of GNSS receiver in the past. Using the pseudo-range measurement value of at least 4 different visible satellites at the same time, the receiver can realize three-dimensional absolute positioning, speed measurement and timing; but Because it contains various errors such as clock error and ionospheric delay, the observation noise is large, and the multipath interference has a greater impact on it, and the accuracy is m-level. ...

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Problems solved by technology

[0004] 1. If the error of the initial value of the code pseudorange used in smoothing is relatively large, it will be difficult to eliminate this error in the subsequent smoothing process, so even if the code pseudorange is smoothed, the accuracy is not high;

[0005] 2. In complex receiving environments such as "urban canyons", the signal is easily blocked, and the carrier tracking loop of the GNSS receiver is prone to signal loss of lock and phase loss of cycle, which leads to a large change in the measured value of the carrier phase, so that The application of this method is limited

[0006] 3. In theory, as the observation epoch increases and the smoothing process advances, the accuracy of the smoothed code pseudo-range gradually approaches the accuracy of the carrier phase. However, the impact of the ionosphere on the code pseudo-range and carrier phase is reversed. When When the number of smoothing processing cycles increases gradually or the ionosphere is disturbed, the smoothing value of the single-frequency pseudo-range will diverge

Although the existing technology proposes to use the Kalman filter as a tool for carrier phase smoothing code pseudo-range, the measurement noise variance of the traditional Kalman filter is constant, and it cannot be well suited to the environment in dynamic GNSS positioning. changes, so that the ideal smoothing effect cannot be achieved

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