DIRECT LEAST SQUARE ROBUST ESTIMATION METHOD FOR ELLIPSE FITTING
Xu Zhengwen 1) ; and Yao Lianbi 1,2)
1)Department of Surveying and Geo-Informatics, Tongji University, Shanghai 2000922)Key Laboratory of Advanced Surveying Engineering of SBSM,Shanghai 200092
Abstract：Tunnel cross section deformation ellipse reflects the deformation of tunnel segment under external load. The spatial geometry parameters of the deformation ellipse can be calculated through accurate spatial ellipse fitting. The algorithm for direct least square ellipse fitting based on robust estimation is introduced, which integrates the gross error detecting by robust estimation and conic parameter constraint of ellipse. The algorithm is implemented in a Matlab program, and is validated by a set of real surveying data of Shanghai Yangtze River Tunnel. The fitting result shows that the algorithm increases the accuracy and the efficiency in gross error detecting.
