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.
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.
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.
KEYWORDS: Data modeling, Global Positioning System, Geomatics, Solar processes, Data centers, Lithium, Geoinformatics, Receivers, Current controlled current source, Astatine
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.
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