Abstract: Global Positioning System is widely used in geodesy and survey engineering. With the development of GPS, precision becomes more and more important for surveying. For GPS control network, baseline solution precision is the basic factor of the control points precision. Basing on the precision of baseline solution, the adjustment of GPS network precision is also important.Baseline solution is the key step of static GPS surveying. The precision analysis of baseline solution result under every condition is benefit to improving GPS survey precision. In this dissertation, GPS baseline solution precision is analyzed since the following aspects: 1, Different length baselines are processed and analyzed by single frequency model and ionosphere free model. 2, Basing on current single point positioning precision, certain coordinate error is added into fixed points to study the result. 3, Baseline is processed and analyzed with different observation vectors and their lineal combination models. 4, 24 hours' observation was divide up to process baseline.In order to save working time and increase working efficiency, sometimes different type of GPS equipments are used, baseline vectors are processed by different software, observation is taken in different time, observation is taken under different condition, several smaller networks of different grade are united to adjust and so on. As the result, there will be different type of observation data in adjustment and the baseline vectors' weight will be unreasonable and the result is not correct. Variance component estimation is a good method to resolve the problem. So the dissertation researched how to apply Helmert variance component estimation into GPS network adjustment, according to adjusting the baseline vectors' weight to increase the precision. The dissertation turns out the software of Helmert variance component estimation and applied it into Sutong Bridge GPS control network adjustment. The control points' coordinate precision are increased, it shows that Helmert variance component estimation is valuable to GPS control network adjustment in practice…

Key words: GPS control network; baseline solution; precision analysis; ionosphere; lineal combination; adjustment of GPS network; Helmert variance component estimation; precision factor

# Analysis of GPS Baseline Precision and Variance Component Estimation of GPS Control Network

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