Research On Precise Attitude Determination Based On GNSS Antenna Array

With the development of surveying and mapping science and technology,the mobile measurement system based on vehicle carrier has achieved rapid development,which puts forward higher requirements for the determination of the attitude information of the moving carrier.Continuous,reliable and high-precision position and attitude information is the key data for the navigation and control of the moving carrier.Global Navigation Satellite System(GNSS)has gained wide attention in GNSS attitude measurement due to its advantages of real-time,continuity and high precision.Compared with INS,GNSS antenna array Inertial Navigation System(INS)has advantages such as easy solidification,immunity from gravity,non-accumulation of errors over time,and attitude accuracy can be evaluated.High precision attitude information can be obtained by using GNSS antenna array to solve the carrier attitude.This paper takes the vehicular GNSS antenna array as the research object,and focuses on the baseline and attitude determination of GNSS antenna array in static and complex dynamic environments.The main research contents and conclusions are as follows:(1)Analysis of GNSS antenna array attitude determination algorithm.The coordinate system and its transformation relation,attitude representation method and attitude parameters are studied in the process of attitude determination.The direct method and least square method of GNSS antenna array attitude determination and accuracy estimation model were analyzed.In order to verify the reliability and accuracy of the two attitude determination algorithms,the attitude calculation of three antenna array and four antenna array was carried out using the measured vehicle experimental data,and the error statistical analysis was carried out on the accuracy of the two GNSS antenna array attitude determination algorithms.The results show that the GNSS antenna array can achieve high attitude solving accuracy,and the length and solving accuracy of the baseline vector play a decisive role in the attitude Angle solving accuracy.(2)Analysis and research on the accuracy of baseline vector calculation in different positioning modes.Two positioning modes,Moving-Base and Kinematic,are used for baseline vector calculation.The error analysis results show that the baseline solution in Kinematic mode is affected by many external factors in a complex continuous dynamic environment,and the baseline solution accuracy is 0.03 m.Moving Base mode can increase the correlation between antennas and further weaken the effects of ephemeris error,tropospheric delay error,multipath effect error,and ionospheric delay error.The baseline vector resolution accuracy can reach 0.003 m,improving the accuracy and reliability of attitude resolution.Based on the error statistics of the baseline vector,select the best two baseline vectors to form a GNSS three antenna array,and all four pairs of antennas to form a GNSS four-antenna array.(3)Analysis and research on attitude solution accuracy of different positioning modes.Based on the vehicle GNSS antenna array and high-precision INS measured data installed on the same platform,the Inertial Explorer software and Moving-Base positioning model and Kinematic positioning model were used to calculate the poses of the three and four antenna arrays under static and dynamic conditions.For Moving-Base and Kinematic positioning modes,the direct method was adopted for the three-antenna array and the least square method was adopted for the four-antenna array.With GNSS/INS integrated navigation attitude determination results as reference,the accuracy and reliability of attitude determination under Moving-Base mode proposed in this paper are proved by analyzing the internal and external coincidence accuracy of attitude determination results.Compared with IE attitude solution,Moving-Base positioning model has certain improvement in course Angle,pitch Angle and roll Angle under static and dynamic conditions with three antenna array direct method and four antenna array least squares legal attitude accuracy.The accuracy of the four antenna least square method is higher than that of the three antenna direct method,and it is closer to the high precision GNSS/INS integrated navigation attitude determination.(4)Analysis of the influence of GNSS antenna array layout on attitude Angle solving accuracy.The GNSS antenna array layout is a key factor affecting the attitude accuracy.Based on the attitude Angle accuracy estimation model,the influences of the included Angle and the length of the baseline on the attitude Angle solving accuracy were analyzed.With different values of the included Angle of the baseline,the attitude Angle calculation accuracy also changes.When the baseline length is fixed and the two baselines are perpendicular to each other,the roll Angle error estimation is the smallest,and the attitude determination accuracy is the highest.The variation of pose determination accuracy in the range of 0.2m ～2.0m was simulated to verify the inversely proportional relationship between pose determination accuracy and base line length,and reasonable suggestions on base line length in actual antenna array layout were given.