The Research on Nonlinear Attitude Determination Method of GNSS Multi-antenna Attitude Measurement

GNSS multiple antenna attitude measurement possesses three attitude determination methods, direct solution, nonlinear least squares method and linear least squares method. Normal nonlinear least squares method on attitude estimate realizes linearization of observation equation with additive euler angle error being the parameter, of which the calculation is largely increased and accuracy can be further enhanced. Hence, nonlinear least squares methods respectively based on additive quaternion error, multiplicative euler angle error and multiplicative quaternion error are derived, and detailed calculation procedures and least squares solutions are respectively presented. Finally a simulation experiment is designed to compare and analyze the direct solution, linear least squares method and 4 types of nonlinear least squares method. Conclusions are as follows: (1) direct solution possesses short calculation time consumption, only being available to degree-level navigation application due to low accuracy; (2) the least squares method whose accuracy is higher than direct solution by more than 60%, reaching to 30', and single epoch time consumption is just a little more than direct solution, is available to minute-level navigation application; (3) nonlinear least squares method based on multiplicative error is relatively the best.