CONTROL OF THE ACCURACY OF GEODETIC SATELLITE MEASUREMENTS

Abstract

Satellite technologies of geodetic measurements are characterized by simplicity, accuracy and cost-effectiveness due to a high level of automation. However, the analysis of recent studies highlights a number of problems that need to be addressed in order to obtain highly accurate and reliable satellite determination components.
Among the influences that distort the satellite radio signal and cause its deviation, there are traditionally errors caused by the satellite constellation, environmental influences, and GPS receiver errors. In such conditions, the best measurement mode to achieve high accuracy is the dual-frequency statics method. Partial preliminary processing of satellite measurements is performed during field work using programs supplied by satellite equipment manufacturers. For the final processing, it is better to use specialized scientific programs that contain a program module that determines the baseline vectors using both code and phase measurements. The most accurate method is the relative determination of positions by phase measurements. However, this task is complicated by the need to calculate the entire phase ambiguity, i.e. the number of wavelengths in the distance between the satellite and the receiver.
The models on which the ambiguity resolution is based are linearized parametric coupling equations in the least squares method. At the first step of the equation, real, i.e. floating, vector estimates and their covariance matrices are obtained. In the second step, the initial values of the ambiguities are obtained from the floating solution, where they are real values, and special algorithms are used to transform the real values into close target values. Thus, to obtain a fixed solution to the ambiguity, the corresponding floating solution is used. As a result of the calculations, the program module provides several types of solutions for the baselines. These solutions are further subject to statistical evaluation using such criteria as the coefficient of variance reference variance (RV), the ratio of variances ratio and the root mean square error (RMS).
The result of the final satellite network alignment is the estimates of coordinates and heights of points, baseline elements, and the a posteriori covariance matrix. In addition, the alignment involves matching all measurements, minimizing random and eliminating systematic errors. To control the accuracy of the final results, statistical hypotheses are used and tested against a number of relevant criteria.