Ambiguity Resolution Among Cors Network Reference Stations And Models Of Atmospheric Delay

Ambiguity Resolution among CORS network reference stations and models of atmospheric delay are the foundation of realizing NRTK positioning. They’re also one of the most effective means of building the global or regional tropospheric and ionospheric models. The Kalman filter was used to realize ambiguity resolution among CORS network reference stations in this paper, and characteristics and effects of various atmospheric interpolation models were compared and analyzed. The main research content is as follows.(1)The mathematical theory involved in the process of GNSS was researched, including the sequencial least squares principle and Kalman filter. The mathematical models of double-difference and the method of selecting reference satellite were introduced. Mathematical models, respective characteristics and applicability of three kinds of single-baseline solution were analyzed.(2) Considering the characteristics and errors of temporal-spatial correlation of medium-long baseline among CORS network reference stations, the impact of the solid tide, troposphere and ephemeris error on medium-long baseline were analyzed and quantified.(3)The data preprocess of ambiguity resolution among CORS network were researched, including the sidereal day filter, phase smoothing psedorange observations, detection and repair of cycle-slip. A new method of GPS undifferenced real-time using triple-frequency to detect and repaire cycle-slip was put forword and verified the effectiveness of the algorithm through real examples.(4)Psedorange observations smoothed by dual-frequency phase observations were used to estimate wide-lane ambiguity; Then adapative factor was adopted to check and determine wide-lane ambiguity. The correct wide-lane ambiguity checked by net-shape constraints was put into the ionospheric combination, constructing the appropriate filter and checking the single-frequency ambiguity using the value of Ratio and net-shape constraints. At last, the selection of the initial value of ambiguity, the effect of Kalman filter, the role of net-shape constraints and the fixed-time were all analyzed in detail using measured data.(5)Research on the various atmospheric interpolation models, including DIM, LCM, LIM, LSM, LSC and Kriging model. Then the effect of various interpolation models inside and outside CORS network were compared and analyzed by exact examples. In this experimental area and the inactive inonspheric atmosphere environment, using various interpolation models inside network can achieve good effect. The accuracy of interpolation was within 3 centimeter and the residual was basically less than the half-wavelength of L1 frequency, however, the accuracy of interpolation outside network was respectively decreased.