ACCURACY ASSESSMENT OF DIFFERENT ERROR ADJUSTMENT METHODS IN CLOSED TRAVERSE NETWORKS; STUDYING THE IMPACT OF DIFFERENT OBSERVATION ERROR SETUPS IN DIFFERENT GEOMETRICAL CONFIGURATIONS
- Dept. of Geomatics Eng., Faculty of Civil Engineering & Transportation, U. of Isfahan, Isfahan, Iran
Keywords: Surveying Network Adjustment, Least Squares, Transit, Bowditch, Doubly-braced Quadrilateral, Error Propagation
Abstract. Similar to all infrastructural works, in order to directly prepare a map, one must act in a whole-to-part way. First, a framework containing certain coordinated points which can be used as base points for subsidiary measurements must be provided, relying on which various surveying tasks can be carried out. By means of solutions, the observation errors in determining the stable points should be propagated between all the observations. In the past, classical methods have been used due to the lack of facilities that can perform numerous calculations in a short time. In this project, we analyzed the accuracy of traditional or classical methods of error propagation in comparison with the Least Squares using simulated observational data with different accuracies. Then, with the output of different methods, the error ellipses are drawn, according to which, these outputs are compared with each other in terms of accuracy. Bowditch method resembled the results of the Least Squares in many cases while Transit method generally showed poorer accuracy and a dependence on the direction of the adjustments. Bowditch method was found to be getting closer to or even more accurate than the Lest Squares when increasing. The whole methods reached a better performance when the accuracy of angular and longitudinal observations were of the same order. Moreover, the Doubly-braced Quadrilateral and the Least Squares with constant weight were of equal accuracies, however, the accuracy of the true-weighted error propagation method outperformed the other methods.