Study Of Determining Jiaozuo Quasi-Geoid

The refinement of Jiaozuo City region quasi-geoid can project the differencebetween the height anomaly with centimeter-level precision, then can achieve thethree-dimensional positioning with the GPS physical sense,take the place of the lowprecision leveling and trigonometric leveling. This will be substantially reduce theworkload of the outside level measurement, reduce the basic scale maps measuringcycle time and speed up the geo-spatial basic framework pace of building "digitalJiaozuo”.Jiaozuo City has various types of landforms and its terrain is from northwest tilt tosoutheastand the GPS/leveling points distribution of Jiaozuo City has regionaldifferences and the resolution and accuracy of the quasi-geoid has clear regionalcharacteristics. In order to take full advantage of the known data and improve the fittingaccuracy, the quasi-geoid of this city will take partition fitting method. The partitioningintroduces the analysis of the abnormal elevation DEM slope. The research willcombine those test results of plane fitting with the overall topography situation ofJiaozuo City to conduct a comprehensive analysis, then using the contour method,comparative law and fitting method to divide the Jiaozuo City into four partitions. Afterpartitioning, four partitions have its single terrain, then GPS/leveling data network willwell-structured which provide protection for determining the high precision regionquasi-geoid.This study main adopt geometric fitting method and global gravity model EGM96geometric fitting method, and the function model adopt plane function and quadraticpolynomial surface function model. After a comprehensive analysis about how muchthe degree of accuracy, outside fitting and the height fitting of each test point can meetthe requirement, then determine the best-fitting model for each region. The fittingaccuracy of the best fit model fitting for different partition can achieve the commonstandard of measure requirements and meet the need of engineering measurement toreplace the leveling which is below the four.For the above study, appropriate fitting model for each partition was initiallyidentified and made a detailed analysis about factors of different area which may havean effect on the precision of quasi-geoid. Then put forward several advises to improve the precision of that regional quasi-geoid and provide the basis for building andprecising the quasi-geoid of Jiaozuo City.