Study On Atmospheric Precipitable Water Estimation Using Ground-based GPS And Water Vapor Tomography

China is a country with more floods, the monitoring and prevention andtreatment of floods have became more and more concerned by whole society in recentyears. Obtaining floods varitions with GPS technology for warning forecast has animportant significance for national economic development and social harmonious.Rainstorm is a key factor leads to floods, and real-time monitoring of watervapor in the troposphere plays an important role in rainstorm forecast. Precipitablewater vapor(PWV) time series with quasi-real-time, high-precision, high spatialartemporal resolution can be obtained by GPS technology, given the uniqueadvantages of GPS technology, combing with high effective data processing softwareand rational tomography algorithm, it has made GPS technology become an importantmethod for observing changes in atmospheric water vapor. This article has beenresearched around with the core issue of water vapor changes in the atmosphere. Weprogramming for calculating PWV, and realizing the analysis of PWV and climaticconditions basd on Matlab software. We also get tomographic troposphere for furtherobtaining three-dimensional distribution of atmospheric water vapor information. Amethod of tomography using anti oblique projection function to encrypt the wet pathdelay was proposed to resolve probable rank deficient case in equation solver. Theprincipal results are as follows:(1) The issues of optimal model selection in the process of calculating PWV,main problems when using radiosonde data for PWV, as well as factors whencalculating zenith tropospheric delay (ZTD) were discussed.(2) Caculating PWV experiment is performed basing on ground-based GPS data.Zenith wet delay is obtained through zenith total delay calculated by GAMIT/GLOBKsoftware and hydrostatic delay calculated by models. By contrasting PWV calculatedwith radiosonda data, the result shows that the difference is very small between twomethods and proves the correctness and feasibility.(3) The key issues about tomography method are discussed. Back-projectionmethod is introduced according to the probable rank deficient case of equation.Tomography method of kalman filter is introduced and got a beeter result based oneffectiveness of kalman filter to calculate the estimated process state.(4) Tomography experiment of ground-based GPS is performed. The correctness and flexibility of this method has been proved by analyzing results in several aspects:three-dimensional distribution of atmospheric water vapor above stations, water vaporprofiles, water vapor changes with time and so on. Finally, calculating PWV of acertain location based on IDW method and comparing with known data, a better resultis obtained.