Studies On The Key Technologies In Tropospheric Water Vapour Tomography Using Ground-based GNSS

Aiming at the key problems that need to be solved in tropospheric water vapor tomography, the article makes studies on the set up of local model for weighted mean temperature of the atmosphere for areas lack of soundings data, the usability of MART for solution of tomography equations, and the fusion of signals from COMPASS and GPS navigation satellite systems for water vapor detecting.1. To solve the problem that the empirical formula of Tm-Ts cannot be set up for areas lack of soundings data, the Kridging interpolation method and reanalysis data ERA-interim have been developed respectively, the reason for no difference between the precison of seasonal and year Tm-Ts model is analized. The studies show that the Bevis Tm-Ts model is more suitable than local model in northeastern China and Qinghai-Tibet Plateau, furthermore both the Kridging interpolation method and reanalysis data ERA-interim are effective in the setting up of local Tm-Ts model for areas lack of soundings data.2. To avoid the trouble of matrix inversion and data organization in LSM, the paper discusses the usability of MART for solution of tomography equations. The existing δ and σ parameters calculated from slant wet delay can only evaluate the precision of the voxels penetrated by slant paths. The paper adds two new statistical parameters Bias and RMS, calculated from wet refractivity of the total voxels, to evaluate the precision of total grid more comprehensively than δ and σ. The paper discusses the effect of the initial field, grid model and Gaussian interpolation in MART on the tomography results based on δ,σ, Bias and RMS. The studies show that in order to obtain good tomography results, initial value should be obtained with accuracy as high as possible, good grid model containing more SWDs with high elevation angle should be designed and Gaussian interpolation method can be used to update the wet refractivity of voxels not penetrated by any SWD. The comparision between MART and LSM is given, indicating that the MART can achieve more stable tomography results than LSM judging from σand RMS.3. Chinese COMPASS satellite navigation system has been providing regional formal service for China and surrounding areas at the beginning of2013. By the end of August15,2012there are13on-orbit satellites. The improvement effect of infusion COMPASS+GPS signal on tropospheric wet refractivity tomography result and the feasibility of pure COMPASS system for tropospheric wet refractivity tomography are discussed for the first time. The findings show that because the now on-orbit COMPASS GEO and IGSO satellites are mainly covering China and surrounding areas, the effective SWDs from nine COMPASS satellites (PC01,PC03,PC04,PC05,PC06,PC07,PC08,PC09,PC10) are comparative to that from GPS. Infusion COMPASS+GPS signals can not improve the tomography result for Shenzhen and Hongkong GNSS network, and the precision of tomography result only using COMPASS signals is superior to that using GPS.