Accuracy Assessment Of Multi-Frequency And Multi-GNSS Velocity Estimation With Time Differenced Carrier Phase Method

GNSS velocity measurement has important theoretical significance and practical value in the fields of aerospace,earthquake early warning,hydrological measurement and so on.At present,most scholars have studied GNSS speed evaluation based on single system or double system,multi GNSS combined velocity measurement and the comparison of velocity measurement accuracy at different frequencies of GNSS.With the full completion of BDS system in China,Galileo,GLONASS,GPS and other systems have been improved and perfected.Satellite navigation has entered the era of coexistence of multiple systems.Multiple systems and multiple frequencies provide new technical conditions for the accuracy and reliability of GNSS velocity measurement.It is necessary to further evaluate the accuracy of multi frequency and multi GNSS.In order to solve the above problems,this paper focuses on multi frequency and multi GNSS time differenced carrier phase,velocity measurement.The main contents and achievements are as follows:1)This paper introduces four classical GNSS speed measurement methods,compares the principles of each speed measurement model,analyzes and compares the speed measurement performance of the four methods with static and dynamic data,and summarizes the applicability of each speed measurement method.2)The accuracy of GNSS velocity measurement is analyzed.The results show that the speed measurement accuracy of different frequency points is different.The speed measurement accuracy of B1 I,B1C,B3 I and B2 a frequency points of BDS system is equivalent to that of E1,E5 a,E6,E5 b and E5 frequency points of Galileo system,and the horizontal direction and elevation direction are better than 1.5 mm/s and 3 mm/s respectively.BDS system B2 I and GPS system L1,L2,L5 frequency point velocity measurement accuracy is equivalent,the horizontal direction is 1.5-2 mm/s,the elevation direction is 3-4 mm/s.GLONASS system G1,G2 frequency point velocity measurement accuracy is the worst,the horizontal direction is 3-4 mm/s,the elevation direction is 5-5.5 mm/s.In addition,the ionospheric free combination of two frequencies will amplify the observation noise,and the accuracy of velocity measurement is lower than that of single frequency.3)The accuracy of the speed measurement of single system and multi system combination is analyzed and compared.The combination of multiple GNSS increases the number of visible satellites,reduces PDOP value and can significantly improve the speed measurement accuracy.Compared with single GPS system,the accuracy of GPS/BDS/GLONASS/Galileo combined speed measurement is increased by 40% in horizontal direction and 46% in elevation direction;when the cutoff height angle is 40 °,the speed in horizontal direction is better than 1 cm/s and the velocity availability rate of elevation direction is better than 2 cm/s from 48% to 98%.4)The accuracy of carrier phase velocimetry in a solar cycle is analyzed.The results show that the accuracy is related to the intensity of solar activity.The more intense the solar activity is,the worse the accuracy is.The difference of velocity measurement accuracy between the peak year and the low peak year is 4 mm/s.The accuracy of GPS L1 frequency and L2 frequency in one solar cycle is compared and analyzed.In the low peak year of solar activity,there is no significant difference between L1 and L2,which is less than 0.5 mm/s.In the peak year of solar activity,the difference between L1 and L2 is 1 mm/s.