Study On The Optimum Method Of Quasi - Geometric Method Of Small Range

Global Positioning System (GPS) is a global satellite navigation and positioning system, which was completed by the Military of America in the1990s,With the advantages such as needn’t intervisibility between the observation points, short observation time,high positioning accuracy, providing three-dimensional coordinates,all-weather work and simple operation and so on, these are excellent than traditional measurement methods. The technique has been used widely in related areas of the engineering construction and other fields of the production and life, but also has replaced most of the traditional measurement.GPS technology is so efficient and can obtain3-D coordinates easily in short time, although it has showed its superiority in the plane precision, but the height of GPS observed belongs to the coordinate system of WGS-84,it is ellipsoid height or geodetic height belongs to the system of reference ellipsoid and no practical significance,rather than the normal height belongs to the quasi-geoid for use of engineering project in our country. Therefore the GPS technology has met the great challenge of reality, In order to use the GPS technology in practice, the conversion relationship between the geodetic height of GPS and the normal height must be studied.Based on the study and grasp to the latest theory of the GPS development, a comprehensive set of principles and common methods of GPS elevation fitting has been introduced in the paper, for surface field such as quadric surface, weighted average, polyhedral function method, the finite element method, moving curved interpolation and BP neural network method etc all have been researched mainly. While for the band area, several methods of curve fitting are also researched.take different engineering project as examples, the corresponding methods introduced above has been used in different terrain and topography respectively, and the fitting accuracy of various methods are compared. Finally, the most suitable fitting method has been obtained to three different topographic conditions in minor region, and providing some guidance for the geodetic refinement to other project in the future. Finally, some standards to check the precision of GPS/leveling network and the measures to improve the fitting precision are proposed.