Study On Acceleration Estimation Method Based On BDS In Airborne Gravity

Airborne gravimetry measurement is one of the effective ways to determine the regional gravity field with aircraft quickly and economically,and it can obtain the middle and high frequency components of the earth gravity field.Also,airborne gravimetry is an important data source for the establishment of a high-resolution and high-precision earth gravity field model,so it has been widely and deeply studied.The current research on the determination method of carrier acceleration in airborne gravity measurement is mainly based on GPS.With the continuous development of BDS,the high-precision estimation of acceleration in aviation gravity measurement based on BDS satellite navigation system becomes urgent and useful.This article draws on the related research of GPS system,mainly including the following work content and research results:1)The basic principles and mathematical models of aviation gravity measurement are expounded.Based on this,the accuracy requirements of GNSS in aviation gravity measurement are analyzed deeply.2)The basic theory of high-precision carrier acceleration estimation based on the single base station difference method of BDS is systematically introduced,and the mathematical model of the method is derived in detail.In-depth discussion of the various sources of error that affect the accuracy of acceleration estimation,including the characteristics of the impact of acceleration,such as cycle slip,ambiguity,ionospheric error and satellite ephemeris error in the position difference method,the ambiguity of the entire cycle must be accurately fixed,otherwise it will have a greater impact on the accuracy of acceleration estimation;The key in the phase difference method is the accurate detection and repair of cycle slip;The residual error of the ionosphere after the difference will increase with the extension of the baseline,and the application of the single base station differential method under long baseline conditions is limited;3)The mathematical model of the doppler observation based on BDS to estimate the acceleration method is deduced.The characteristics of the error sources such as satellite position error,satellite velocity error,receiver position error and observation noise that affect the accuracy of the method are analyzed.Satellite position error,satellite speed error and receiver position error can be greatly reduced or eliminated by the difference method.Observation noise has the greatest influence on the accuracy of the acceleration,reaching the level of m Gal;4)Aiming at the limitation of the single base station difference method and the doppler method in the non-base station coordinated observation area,a precision single point positioning acceleration method based on the BDS is proposed.The precision single-point positioning algorithm uses carrier pseudorange observations.When there is no reference station,the static measurement accuracy can reach the centimeter level,and the dynamic measurement accuracy can reach the decimeter level.The main error sources and their impact characteristics of acceleration estimation using this method are analyzed in depth.The results show that the influence of ephemeris errors on the acceleration estimation results is negligible,but due to the convergence speed of Kalman filter,the post-mortem precision ephemeris is a better choice;Different types of clock-difference products with 30 s sampling intervals issued by various agencies have little effect on the acceleration estimation results;5)Finally,using the ship survey data of the South China Sea,the single base station differential method,doppler method and precise single point positioning method based on BDS were tested and verified.The results show that the phase difference method has the best accuracy,the accuracy of acceleration determination is better than 2m Gal under dynamic conditions,and the position difference method is within 3.5m Gal.The calculation results of the precision single-point positioning method based on BDS have good consistency with the phase difference method and the mutual difference is about 1.5m Gal,which also verifies the feasibility of the precision single-point positioning method based on BDS in high-precision estimation of carrier acceleration;The doppler method has the worst accuracy and due to the large observation noise under dynamic conditions,the acceleration error reaching 7?10m Gal.