| Summary: | 碩士 === 中興大學 === 土木工程學系所 === 99 === GPS has been used widely in all kinds of engineering, the traditional measurement of plane surveying has been replaced, but datum of leveling is restricted the inconsistency between the two elevations, GPS technique, which obtains ellipsoidal heights, can not be directly used in the leveling height system, it must be transformed by appropriate geoid model, and then can be used in engineering survey. Therefore, researchers have been so far devoting themselves to geoid study in domestic and abroad.
Due to geographical environment''s impact in Taiwan, gravity and leveling are not easy to survey, hence a lack of reliable data. The representation of the result is poor in geoid model of Taiwan, all the results are fit to large area, but small area are not. The geoid, which can be used to reflect the circumstances of its spatial distribution by mathematical functions, is changed unobviously in a specific area, it obtained other by interpolating. A local geoid model is established by the study, which is based on GPS and leveling data with least squares support vector machine.
According to the experiment, the result of using LS-SVM with Radial Basis Function (RBF) kernel and the third-order polynomial kernel computed that the accuracy is about ±1.4 cm, it could satisfy the requirements of elevation in engineering survey. Comparing with the results by zoning, RBF kernel is better than others. The obtained results from this study would be a great help in improving spirit leveling in the future, as well as enhance GPS technique.
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