Research On GNSS Multi-antenna Baseline Solution On The Mobile Platform

Attitude information is an important navigation parameter for vehicles,the precise attitude determination with multiple antennas on the mobile platform is a new developing technique in recent years,it has broad application prospect in airborne gravity,mobile mapping,marine exploration and development.With the limitation of the mobile platform,baselines between multiple antennas are only a few meters,and then the accuracy of baselines has a great influence on the accuracy of attitude determination,consequently,the key of the precise attitude determination with multiple antennas on the mobile platform is how to obtain the high precision baseline vectors for each epoch,that is to say how to solve ambiguities correctly from each baseline for each epoch is crucial for GNSS multi-antena attitude determination.In view of this.problem,the main contribution of this paper is as follow:(1)Researches on mathematical models of GNSS dynamic short baseline networkThe location parameters and the ambiguity need to be resolved simultaneously for the GNSS short baseline resolution for single epoch in precision dynamic solution.however,the main difficulty of kinematic positioning only using high precision carrier phase observations is that normal matrix is rank deficeny and it could not solve all parameters directly;Because of the low accuracy of pseudorange which is generally 1/100 of the accuracy of carrier phase,the normal equation is ill-posed using carrier phase with pseudorange,the float ambiguities is far away the correct ambiguities and the search space is larger,the success rate of searching for correct ambiguity is low accordingly.The key is how to obtain accurate priori information of approximate coordinates or baselines vectors.To address this problem,a two-step method of the short baselines resolution is proposed in this paper using multiple antennas on the mobile platform as a mobile network.Firstly,on the basis of the character that wide lane observations have long wavelength and wide lane ambiguities is easy to fix,besides based on the advantages that the location relationship among multiple antennas is fixed and some baseline length is accurately known in advanced,the wide lane ambiguities from all baselines are solved simultaneously with the baseline length constraint,dm-cm level accuracy of all baseline components can be obtained.Secondly,base frequency ambiguities are resolved simultaneously with the wide lane approximate baseline components constraints obatained from the first step,and the cm-mm level accuracy of baseline vectors can be gained.(2)Researches on the ambiguity test of baselines in dynamic conditionBecause ratio value is a statistic index based on the sample size to infinite.But the magnitude of the observations is very small for the kinematic positioning.as a consequence,it is not always reliable.In order to enhance the reliability of ambiguity test,with the fixed relationship between muti-antenna baseline network and the priori constraints for baselines.Consequently,A comprehensive judging criterion combined baseline error,mean square error of weight unit,the closed loop of baseline network and ratio value is designed,which can avoid that the wrong ambiguity is accepted or the correct ambiguity is rejected because of the unreasonable ratio value.