Research On Method Of Quasi Geoid Refinement And Its Application In Tongliao Baixingtu Area

Since its emergence,GPS technology has quickly become an indispensable tool for measurement with its global coverage,high accuracy,real-time positioning,freedom from climate constraints,and good anti-jamming.Including RTK technology and CORS systems that were later derived from GPS technology.GPS technology has been greatly promoted and applied in the field of plane measurement.At the same time,the accuracy has reached the level of centimeters or even millimeters.However,GPS technology is not satisfactory in the aspect of elevation measurement.It is mainly due to the inconsistency between GPS measurement and China's elevation system in terms of the base surface,Finding the height anomaly and directly converting the GPS geodetic height into the fixed height have become the focus of attention in the field of surveying,which is also converted into the problem of quasi-geoid refinement.Considering that the more common and accurate method of quasi-geoid refinement is to use gravity data,but gravity data is classified information in China,it is difficult for ordinary surveying and mapping units to obtain gravity data.The author tries to study the refinement method of quasi-geoid without gravity dataBased on the background,the author has reviewed a large number of relevant documents,summarized the current research situation at home and abroad,The elevation system,elevation datum and the technical method of quasi-geoid refinement in China are studied.The plane model method,quadric surface method and cubic surface model method in geometric method are analyzed,and the combination method considering EGM2008 model is studied.Then the precision control in quasi-geoid refinement is analyzed.In the third chapter about application,the three geometrical methods of planar model method,quadric surface model method,cubic surface model method and the combination method of EGM2008 model are applied in the Tongliao baixingtu area,and 25 points with GPS / leveling data are designed.Among them,the quadratic surface model method and the cubic surface model method are divided into AB schemes.Through these four methods and six schemes,The results show that the fitting method can fit the GPS elevation of the survey area well,but the location of the fitting point has a greater impact on the fitting results.The location of the fitting point is evenly distributed,and the fitting results are closer to the true value when the distance from the fitting point is closer.At the same time,the quadric surface model method and the cubic surface model method are more accurate and reliable than the plane model method.Considering the EGM2008 model quasi-geoid refinement method,the accuracy of the checkpoint is obviously improved,and the gross error data is eliminated,which is more suitable for the high precision requirement.