BDS/GNSS Multi system Fast Star Selection Algorithm Using GDOP Impairment Estimation
How to balance the calculation data volume and data solution speed in the system while ensuring the positioning accuracy of the global satellite positioning system is currently a hot topic of discussion.The Sherman-Mor-rison formula was used to decompose the calculation formula of GDOP value and correlate it with the number of satel-lites to obtain the impairment estimation formula of GDOP value and the change of satellite number.Further,the GNSS fast star selection algorithm using GDOP impairment estimation was proposed by combining the GDOP impair-ment estimation formula with the classical type selection star selection method(maximum volume method).The basic idea of the algorithm is to first use the maximum volume star selection method to obtain four initial benchmark stars,and then use the GDOP impairment estimation prediction formula to select visible stars to reduce the GDOP value and improve the overall stability of the algorithm.By setting an accurate threshold,the autonomous star selection can be completed without any intervention.The verification of the measured data shows that:(1)when 13 visible stars are involved in the calculation,the GDOP values of the calculation results of the fast star selection algorithm using the GDOP impairment estimation are not more than 2,which fully meet the requirements of high-precision positioning;It can be seen that when the number of stars participating in the calculation continues to increase,the GDOP impairment is no longer obvious,but the calculation time has increased significantly;(2)After setting the threshold value of the calculation result of the GDOP impairment estimation formula,the star selection algorithm can achieve the adaptive function.When the GDOP impairment valuation threshold is 0.01,the number of visible stars participating in the cal-culation for most epochs does not reach 13.When the number of selected stars reaches 13,GDOP is less than 2 under 93.54％ probability,which further shows that the autonomous star selection algorithm using GDOP impairment estima-tion can meet the requirements of high accuracy.
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