Research On Ambiguity Resolution Based On BDS Triple-frequency

In the background of the rapid development of BDS,higher positioning accuracy is required.While the accurate fixation of ambiguity is the necessary prerequisite to realize the precise positioning.In view of the advantage of broadcasting navigation signals on three frequencies,it is necessary to research on ambiguity resolution based on BDS triple-frequency.In this paper,main effort is made on the selection of BDS triple-frequency optimal combination observations,the theory of triple-frequency cycle-slip detection and repair,the method of triple-frequency ambiguity resolution as well as its reliability test.The contents and achievements are summarized as follow.1.According to the various error characteristics of the combination observations,the criterions of picking up the optimal observation combination coefficient are researched.Filtering the observation combination of BDS,the conclusions are concluded as follow.The size of combination wavelength is inversely proportional to the lane number.The longer combination wavelength is,the larger geometrical error of combination observation is.The combination observation with weak ionospheric characteristics tends to a short wavelength.There is no combination observation what has minimum ionospheric delay amplification coefficient and minimum observation noise amplification coefficient at the same time.The sum of the combination coefficients of the optimal combination observation with long wavelength,weak ionospheric delay and low observation noise is generally 0,-1 or 1.2.The methods of cycle-slip detection and repair are analyzed based on MW combination and triple-frequency pseudorange and carrier phase combination.In view of the situation that active ionosphere or large observation interval,the triple-frequency STPIR combination is combined with MW combination and triple-frequency pseudorange and carrier phase combination to detecting and repairing cycle-slip.Under large sampling interval,when cycle-slips occur on a single frequency or multiple frequencies,the detection and repair effects of both methods are analyzed and the solution of cycle-slip reapir's inaccuracy is given.Results indicate that,two methods have a high detection precision for all cycle-slip under the condition of low sampling rate.3.The main errors of the classical TCAR method and the factors which affect the long baseline ambiguity resolution are studied.An improvement scheme is put forward according to these limiting factors.The scheme can improve the Narrow-Lane ambiguity resolution using comparative analysis.4.In order to solve the problem of low success rate of Narrow-Lane ambiguity resolution under long baseline condition,ionospheric delay correction method is introduced.It is found that the method eliminates the influence of the first order ionospheric delay error,but it amplifies the observed noise.The results show that the method can improve the accuracy of long baseline ambiguity resolution using a certain epoch data smoothing.5.The theory and importance of ambiguity resolution reliability test are discussed.In term of the inherent statistical characteristics of the ambiguity floating solution,the formula for calculating the success rate of ambiguity resolution is deduced based on direct rounding method,the Bootstrap method and least-squares estimation.The method of Ratio test based on reliability index is introduced.