As the fact that most of the ground-based GPS lacks of the detection of the upper-air meteorological data, thus the application of ground-based GPS sensing of water vapor technology has been limited due to the inaccurately calculated weighted mean temperature. In that case, this paper has studied and analyzed the methods of obtaining weighted mean temperature by deriving the data from GGOS Atmosphere weighted mean temperature grid data in Xinjiang. By using the radiosonde data, this paper has evaluated the accuracy of the weighted mean temperature(GTm) derived from GGOS atmosphere weighted mean temperature grid data and considering the seasonal and geographic factors , we employed a correction model to fit the residuals of GTm. Results show that the GTm derived from mean value interpolation and corrected by correction model meet the requirements of ground-based GPS precision sensing of Water Vapor in Xinjiang ; The inner average precision RMSD is 2.33K , MAE is 1.80 K; The outer average precision RMSD is 2.36K , MAE is 1.85 K.
In order to study the applicability of the elevation model with considering terrain fluctuation factor in the calculation of the atmospheric water vapor conversion coefficient, this article selects different elevation data for five years from Xinjiang region sounding stations, using elevation model and Emardson model without considering the terrain fluctuation to calculate water vapor conversion coefficient K, and analyzing the applicability of the elevation model in Xinjiang region where is a large area of terrain, then comparing the accuracy of the conversion coefficient between the same latitude and different elevations as well as between the same elevation and different latitudes by the elevation model, researching the influence on elevation model from station’s latitude and altitude. The research shows that: (1) Adding terrain fluctuation factor of elevation model and Emardson model without considering the effects of elevation will appear the phenomenon of increasing accuracy, and precision of elevation model is slightly better than that of Emardson model with station’s altitude increasing. (2) When latitude acts as influence factor, the lower latitude the measuring station is, the higher accuracy of the elevation model will be. When elevation acts as influence factor, the bigger elevation the measuring station is, the higher accuracy of the elevation model will be. (3) The applicability of elevation model is better in these regions which located in low latitude and high altitude.
Klobuchar model can reflect the spatial and temporal variations of ionospheric feature, but model fixed initial phase and night-time delay will introduce a large number of errors. Aiming at the shortcomings of the models, take least-squares surface fitting model as the background, using CORS network in Nanning region to measure the data correctly, the Klobuchar model's initial phase, amplitude, and night-time delay values are steadily corrected, so as to establish regional ionospheric model in Nanning, the results show that the accuracy of Klobuchar model is improved significantly.
The formation of the ionosphere is mainly the interaction of solar radiation and the earth's atmosphere, in different
temporal-spatial environment, the characteristics of the ionosphere is more complex, and the Total Electron Content
(TEC) is one of the important parameters of the ionospheric morphology and structure. Therefore, in this paper, using the
high-precision TEC time series provided by the International GNSS Service (IGS) as experimental data, by Fast Fourier
Transform (FFT) to detect its periodic changes, and then focus on analysis the characteristics of diurnal variation,
seasonal variation and annual variation and winter anomaly, simultaneous analysis of the ionospheric characteristics vary
with latitude and longitude. The result show that: (1) TEC changes more intense during the day, but the night is quiet,
and in different latitudes, the TEC reached peak value at different moment; (2) Winter anomaly exists only during the day,
night does not exist; (3) In the same time domain, TEC value decreases gradually with the increase of latitude, and it has
different spatial variation features in different hemispheres.
The tropospheric delay is one of the main errors for earth observation and a variety of radio navigation technologies, and the UNB3m model can be used to calculate the zenith tropospheric delay (ZTD) without any real measured meteorological data, which taking the major changes in water vapor profiles with latitude into account, and it widely applied in Wide Area Augmentation System in America. However, there are few researches carried out on the assessment of ZTD from UNB3m model over Asia area. In this study, three years of the ZTD data observed from 56 IGS (International GNSS service) sites distributed in Asia area is used to assess the effectiveness and accuracy of ZTD calculated from UNB3m model. The results are: (1) relative to IGS observed ZTD, the bias and root mean square (RMS) for ZTD calculated from UNB3m model are -0.1 cm and 6.0 cm, respectively. Besides, the bias shows significant periodic characteristics in Asia area. (2) The bias and RMS present seasonal variations, which generally show larger values in summer months. (3) The precision of ZTD calculated from UNB3m model increases with increasing altitude or latitude, and also the bias and RMS show inconsistently in different Asia areas. At last, the best results can be achieved in inland area where presents the mean yearly RMS of 2.4 cm. These results provide a reference for the study of the tropospheric delay correction model and the applications of real-time GNSS navigation and positioning.
Using the eleven Radiosonde Stations’ data in southwestern of China from 2010 to 2013 to calculate the conversion coefficient K which is a reference value of Precipitable Water Vapor (PWV). Then build the EMARDSON model and the EMARDSON K model which introduced with elevation parameter and altitude. And to analysis the accuracy of the two models in the southwest China by radiosonde data in 2014. The results show: 1) The K value calculated by EMARDSON model has good adaptability in southwest region. 2) The method of spatial interpolation prediction by choosing 7 Radiosonde Stations’ K value uniformity is more adaptable than using 11 Radiosonde Stations’ K value to build basic model in the case of predicting 11 Radiosonde Stations’ K value, and it has a certain accuracy when predicting by using spatial interpolation in some areas where lacking data. 3) The accuracy by using the A-EMARDSON model to predict K value was improved obviously. at the same time, when predicting K value by the method of spatial interpolation, both the precision of inner and the precision of outer are better than EMARDSON model. So it can be concluded that the altitude factor is an important factor to influence the K value prediction.
Aiming at the characteristic of nonlinear and non-stationary in ionospheric total electron content(TEC), this article bring Wavelet Analysis into the autoregressive integrated moving average model to forecast the next four days’ TEC values by using six days’ ionospheric grid observation data of Chinese area in 2010 provided by IGS station. Taking IGS station’s observation data as true value, compare the forecast value with it then count the forecast accuracies which are to prove that it has a quite good result by using WARIMA model to forecast Chinese area’s Ionospheric grid data. But near the geomagnetic latitude of about ±20°grid, the model’s forecast results are a little worse than others’ because Geomagnetic activity is irregular which lead to the TEC values there change greatly.