Estimation of satellite and receiver instrumental biases using GPS data

For radio communication systems, navigation systems and short wave implementations using radio waves, free electron content in ionosphere is important. One of the most important parameter to track the changes in ionosphere is Total Electron Content (TEC). By means of GPS data, estimation of TEC is executed safe and economical. TEC values and differential code biases are presented to users via various IGS analyse centers in a low time resolution, but some analyse centers do not supply differential code biases for every day and every station. Differential code biases which supplied by analyse centers, mostly do not change in a day or in a month, but these biases can change in an hour. To have the true TEC estimation, it is necessary to estimate differential code biases and remove them from the measurments properly. In the previous studies, differential satellite biases are acquired by analyse centers and then differential receiver biases are estimated or sum of differential code biases is estimated. In this thesis, composite biases were defined. These composite biases were estimated. For a given moment, using the information that sum of the differential satellite biases is zero estimation is executed in this thesis. Then using composite biases, estimation of Slant Total Electron Content (STEC) and estimation of Vertical Total Electron Content (VTEC) are done. While STEC estimation and VTEC estimation executing, estimated composite biaeses and daily mean of estimated composite biases were used. Proposed method is executed in both quiet and disturbed days and high, mid and equatorial latitude regions. At the end of the day, while receiver stations in mid latitude and high latitude regions give more accurate estimation values both quiet and disturbed days, receiver stations in equatorial latitude region have some deviations. In this thesis, it is observed how change composite biases in a day and in a month. Estimation of differential code biases is done with 30 seconds time resolution. CODE, JPL, IGS and UPC give code biases values with 1 day time resolution. In this state, changes in ionosphere are not observed in detail. Using 30 seconds time resolution values, it is done more accurate VTEC estimation. Keywords: Ionosphere, Global Positioning System (GPS), Total Electron Content (TEC), Differential Code Biases (DCB)