Research On Positioning Performance Of BDS/GPS Combined Single-frequency RTK

The BDS/GPS combined single-frequency Real-time Kinematic(RTK)positioning technology is a real-time dynamic positioning technology that utilizes both the Bei Dou Navigation Satellite System(BDS)and the Global Positioning System(GPS)for combined positioning.This technology is widely used in fields such as surveying and surveying,deformation monitoring,and precision agriculture.Compared with traditional positioning technology,this technology has the advantages of strong real-time performance,wide applicability,and high accuracy.However,adverse factors such as atmospheric delay,environmental obstruction,and multipath effects can lead to unstable positioning results and even problems such as loss of lock and position jump.To improve the positioning performance of this technology,this thesis focuses on key technologies such as cycle slip detection and repair,multipath suppression,and ambiguity resolution and confirmation.The main innovations of this thesis are as follows:(1)In terms of cycle slip detection and repair,the principle and performance of the high-order difference method are described.Aiming at the situation where traditional single-frequency cycle slip processing methods are only applicable to continuous observation epochs and cannot accurately detect cycle slips in non-continuous epochs,an improved polynomial fitting method is proposed.The algorithm determines the sampling interval through loss of lock counting,extrapolates the phase fitting value of the signal to recover the epoch,and uses Lagrange interpolation to interpolate the data during the loss of lock period.Experimental results show that this method effectively overcomes the influence of non-continuous epochs,and can effectively detect and repair cycle slips caused by missing epochs,improving the accuracy and comprehensiveness of cycle slip processing.(2)In terms of multipath suppression,an improved MEDLL algorithm is proposed to address the shortcomings of the MEDLL algorithm in terms of computational complexity,computational load,and real-time performance.This algorithm combines the Teager-Kaiser operator with the MEDLL algorithm,introduces a Teager-Kaiser threshold to evaluate the multipath signal,reduces the computational load,and significantly improves the estimation accuracy and computational efficiency.By setting a detection threshold value,the number of multipath channels and corresponding estimation parameters,including signal amplitude,delay,and phase,can be quickly and accurately estimated,improving real-time performance.The effectiveness of the method is demonstrated through experiments.(3)In terms of ambiguity resolution,an improved partial ambiguity fixing algorithm is proposed to address the problem of misjudgment or omission in subset selection and threshold setting in traditional partial ambiguity fixing algorithms.This algorithm first preliminarily screens the data using the elevation angle and signal-to-noise ratio,and gradually eliminates the ambiguity with the largest variance based on the success rate estimation,until the success rate is higher than the preset threshold,to achieve optimal subset selection.This algorithm can effectively reduce the ambiguity search space,and improve the ambiguity fixing rate and reliability of ambiguity resolution.In terms of ambiguity validation,we combine the threshold of the statistical test and the consolidation domain of integer aperture estimation to comprehensively evaluate the reliability of ambiguity fixing.Experimental results show that the improved PAR algorithm has a significantly higher fixing rate than existing algorithms,with static and dynamic positioning fixing rates reaching 94.96% and 56.7%,respectively.The horizontal and vertical accuracies have been improved by 30% to 45% and 60% to 75%,respectively,and it can effectively shorten the initialization time of RTK positioning and accelerate the convergence speed of the solution.