The Study On Determination Of Quasi-geoid Refining Without Gravity Data

Geiod or quasi-geoid is a height datum for acquiring geospatial information. Determining high accuracy local geoid is the geodesy research hotspot. It will provide mufti-disciplinary research and application such as base map up date,digital China geo-spatial framework, local monitoring on settlement,environment forecast,disaster prevention, national defense construction, ocean science, weather forecast, earth science research, traffic, water resources, power with essential mapping service, has significant scientific significance and tremendous economic and social benefit. Therefore geoid refining is one of important missions for the establishment of the height datum in a country or a region.In the paper, the research development and background in quasi-geoid are introduced simply at first. The basic theory and methods for the determination of geoid are introduced. Then discuss and make a research about geometrical method and gravity method at length respectively, as well as combination methord. Considering that some area are short of gravity data and level points, I summarize the direction of research that the methord based on gravity model to determine the geoid. Combining the idiographic facts, make tests and reaserach based on "Remove-Restore"Method.Then the main error sources for the determination of geoid are analyzed and the error transmission formulas are given.Using the "Remove-Restore" Method,make the design of quasi-geoid model based on gravity model without gravity data.And establish the "GPS/LEVELING HEIGHT FITTING SYSTEM". Basing on it, make a research about the route and approach and mathematic model of precise determination of quasi-geoid. And design the programme of the model. Make a test in Ben xi area and Song yuan Bai cheng area. Demonstrate the feasibility and practicability of "Remove-Restore" technique adequately. Using "Remove-Restore" technique with 4 GPS/leveling points as known points in Song yuan Bai cheng area,which is about 40 thousand sq.km.. The precision achieves 0.2m. Using "Remove-Restore" technique with 6 GPS/leveling points as known points in Ben xi area,which is about 9 thousands sq.km.. The precision achieves 0.001m.. Make some improvement by using "Remove-Restore" technique twice. Make a tset in Ben xi area. The standand deviation enhances 0.002m.Finally get hode of some senseful conclusions.