This paper presents three strategies for modeling the regional empirical T_m (the weighted mean temperature of the atmosphere) to obtain more accurate determinations in a regional empirical model that is better adapted to the geographical and climatic characteristics of the applied area. The proposed models utilize data from four radiosonde stations in Guangxi, at Nanning, Guilin, Wuzhou and Baise, over an 11 month period (from Jan. to Nov. of 2011). The experimental results demonstrated the following: (1) there is no significant difference between monthly and annual regression results at each site; (2) it is more reasonable and feasible to use the proposed regional Hybrid model for the area far away from the radiosonde site; (3) from the analysis of the possible temperature conditions, the precision of the proposed regional Hybrid model is higher than that of the well-known Bevis formula and of some other existing models and can reach an accuracy within 1 mm for the GPS-derived PWV estimates for the applied region.
Tropospheric delay is a primary error source in earth observations and a variety of radio navigation technologies. In this paper, the relationship between zenith tropospheric delays and the elevation and longitude of stations is analyzed using the zenith tropospheric delay final products of International GNSS Service (IGS) stations from 2011. Two new models are proposed for estimating zenith tropospheric delays from regional CORS data without meteorological data. The proposed models are compared with the direct interpolation method and the remove-restore method using data from Guangxi CORS. The results show that the new models significantly improve the calculated precision. Finally, the root mean square (RMS) errors of the new models were used to estimate the surface precipitable water vapor (PWV) value at CORS station, which was determined to be less than 2 mm.
The estimation of Precipitable Water Vapor(PWV)derived from Global Positioning System(GPS)data at the IGS site WUHN is assessed by comparing with PWV obtained from radiosonde data(No.57494)in Wuhan.The applicability of Saastamoinen(SAAS),Hopfield and Black models used for estimating Zenith Hydrostatic Delay(ZHD)and Zenith Wet Delay(ZWD)and different models is verified in the estimation of GPS-derived PWV for the applied area.The experimental results demonstrated that:1)the precision of PWV estimated from Black model used for calculating ZHD(ZHD B)is lower than that of SAAS(ZHD SAAS)model and Hopfield model(ZHD H)with the RMS of 4.16 mm;2)the RMS of PWV estimated from SAAS model used for calculating ZWD(SAAS)is 3.78 mm;3)the well-known Bevis model gives similar accuracy compared with the site-specific models for T m in terms of surface temperature(T s)and surface pressure(P s),which can reach the accuracy inside 1 mm in the GPS-derived PWV estimates.
