Construction Of Elevation Benchmarks And Analysis Of Geographical Factors

Unifying global elevation datum is one of the important research objectives of geodesy,especially with the development of global navigation system and satellite altimetry technology and the improvement of precision and resolution of gravity field model,it is possible to unify global elevation datum.When building elevation datum,it is often influenced by the construction method and external environment,which results in the difference of elevation datum between countries or regions.Based on the construction of elevation datum,this paper studies the influence of different geographical factors on elevation datum,so as to decide whether the influence of some geographical factors should be taken into account in the selection of different regions,and to provide a reference technology and ideas for the unification of the construction of elevation datum.This paper first introduces the research background and significance of elevation datum,elaborates the theory and method of building elevation datum,and introduces the method and influencing factors of unified elevation datum.Secondly,it compares and analyses the differences between existing Super-high-order gravity field models.It uses virtual spherical harmonic method to construct geoid in experimental area,and analyses the method in plateau,Basin and plain.And the applicability of hills.Finally,the coefficients of potential models are extracted from different terrain models,and the effects of different geographical factors on different regions are calculated and analyzed.The results of this study are as follows:(1)Taking the EGM2008 model as a reference,the differences between the existing Super-high-order models and the EGM2008 model in the world and China are compared and analyzed.The results show that there are some differences between the three models and the EGM2008 model,and there are obvious maximum and minimum values.The difference between SGG-UGM-1 model and the other two models is smaller than thatbetween EGM2008 model and SGG-UGM-1 model.(2)Based on the spherical crown harmonic model,the regional geoid is constructed by the virtual spherical harmonic method.The virtual boundary bandwidth of the four regions is calculated by using the fine structure information of the geoid,and the existing data and the simulation data are analyzed by using the virtual spherical harmonic method.The results show that the transition bandwidth of Sichuan Basin and Qinghai-Tibet Plateau is small,and the error of constructing regional geoid by virtual spherical harmonic method can reach mm level,which breaks through the limitation of the highest order of traditional spherical crown harmonic model and can approximate the regional geoid infinitely in theory.(3)Comparative analysis of the impact of different geographical factors on the elevation benchmark.Plateaus,hills,plains,basins,and ice fields are selected,and the effects of geographic factors on different regions are directly or indirectly calculated by models.The results show that the influence of bedrock is the largest;in the Qinghai-Tibet Plateau and the Arctic Ocean,the influence of topography is the second;in the southeast hills,the Northeast Plain and the Sichuan Basin,the third is the impact of water on the elevation reference.Second,the impact of glaciers only in the Greenland region is significant,and the impact in most parts of the country is negligible.