Performance Evaluation Of BDS/GNSS Relative Positioning Under Multiple Scenarios

The Global Navigation Satellite System(GNSS)has entered the era of multi-system collaborative positioning as a result of the ongoing innovation and development of satellite navigation systems in several nations.The total number of GNSS satellites in orbit has already surpassed 130,and this increase is good for enhancing location accuracy and dependability.In addition,multi-mode and multi-frequency fusion positioning has emerged as the future trend in satellite navigation positioning as the demand for high-precision positioning in a variety of industries rises.For this reason,it is important to thoroughly assess the performance of multimode and multi-frequency GNSS relative positioning.The following are the key findings and recommendations of this study:(1)The GNSS relative positioning theory is thoroughly explained.The functional model and random model of relative positioning are derived and examined,as is a unified approach of spatiotemporal reference frame for multiple GNSS.The least squares method and Kalman filtering techniques for GNSS parameter estimation are described,as well as the major flaws in the positioning process and the corrective procedures.We present the ambiguity fixation theory and validation techniques in a concise manner.(2)A comprehensive and systematic evaluation of the quality of GNSS data is carried out.The quality of observation data is investigated using indicators such as data integrity,signal-tonoise ratio,multipath effect,cycle slip ratio,pseudo-range noise,and carrier phase noise.The results show that the mean data integrity rate of each station is greater than 90%;that the signalto-noise ratio and multipath error are correlated with the satellite elevation angle,and that the signal-to-noise ratio increases and the multipath error decreases as the satellite elevation angle increases;that the cycle slip ratio values of each station differ,and that the values of CUT0 and PERT are smaller;and that the signal-to-noise ratio and multipath error are correlated with Each station’s pseudo-range noise is different,with the WUH1 station having the highest pseudorange noise of 0.044m;Each station’s carrier phase noise is similar,and all are less than 0.02 cycles.(3)Static relative positioning research on single-system and multi-system combinations is conducted using observational scenarios such as zero baseline,short baseline,medium-long baseline,and long baseline.The results of the experiments show that: 1)multi-system combination outperforms single system in terms of satellite number,position dilution of precision(PDOP),positioning accuracy,and ambiguity fixed rate.The four-system combination has better positioning accuracy than the three-system combination,and the three-system combination has better positioning accuracy than the two-system combination.This rule also applies to the ambiguity fixed rate.2)When the baseline length is less than 15 kilometers,positioning accuracy of better than 2 centimeters in the horizontal direction and 3 centimeters in the vertical direction is achievable,and the ambiguity fixed rate exceeds 97%.3)When the baseline length is between 15 and 100 kilometers,except for the Galileo system,all other single systems and multi-system combinations can achieve horizontal positioning accuracy better than3 centimeters,vertical positioning accuracy better than 6 centimeters,and the ambiguity fixed rate is not lower than 92%.4)When the baseline length exceeds 100 kilometers,the relative positioning accuracy in the horizontal direction of the single system can reach better than 9centimeters,the vertical direction accuracy can reach better than 10 centimeters,and the ambiguity fixed rate can reach 70% or higher.In contrast,the horizontal positioning accuracy of a multi-system combination can reach better than 5 centimeters,the vertical positioning accuracy can reach better than 7 centimeters,and the ambiguity fixed rate can reach 90% or more.(4)A dynamic baseline testing scenario for in-vehicle applications was designed to investigate the performance of single and multi-GNSS system combinations for dynamic relative positioning.Experimental results showed that the four-system combination achieved a positioning accuracy of better than 9cm in the horizontal direction and better than 10 cm in the vertical direction,with the ambiguity fixed rate of over 89%.Compared with the single system,the multi-system combination achieved higher positioning accuracy.Furthermore,the positioning accuracy of the four-system combination was better than that of the three-system combination,while the accuracy of the three-system combination was better than that of the dual-system combination.