A Troposphere Tomography Method by Combining the Truncation Coefficient and Variance Component Analysis

Traditional troposphere tomography method cannot use the GNSS signals penetrating from the side face of research area, which not only decreases the utilization rate of GNSS observation but also leads to a low percentage of voxels crossed by rays. In order to overcome this issue, the GNSS signals penetrating from the model’s side face are also used to build the observation equation by introducing the truncation coefficient in this paper. Due to the fact that the tomography modeling is consists of various equations, including observation equation (using signals from the side and top faces of research area to build equations), horizontal and vertical equations, how to determine the weightings of different equations is a key to obtain the reliable tomographic result. Therefore, a method is proposed to determine the weightings of various equations based on the variance component analysis (VCA). The data from Satellite Positioning Reference Station Network (SatRef) of Hong Kong over the period of 27 days is selected for the tomography experiment. The tomographic result shows that the proposed method is of ability to obtain a good quality. Comparing to the traditional method, the utilization rate and number of voxels crossed by rays have been improved by 32.21 and 12.23%, respectively. When compared to the radiosonde data, the RMS error of the reconstructed integral water vapor (IWV) derived from the proposed method (4.2 mm) superior to that from the traditional method (5.2 mm). The comparison of water vapor profiles also shows that the proposed method with a RMS value of 1.30 g/m³, is smaller than that of traditional method with a value of 1.58 g/m³, and the accuracy of tomographic result based on the proposed method is increased by 17.7%.