The Study On The Effect Of Vertical Deviation In Gravity Survey

In physical geodetic survey,the deflection of the vertical is the angle between the direction of the vertical line of the actual gravity and the normal of the reference ellipsoid,indicating the degree of inclination of the geoid relative to the reference ellipsoid,which is important for the refinement of the geoid.But it is usually ignored because of the value of the vertical deviation is extremely small.With the realization of accurate measurement of vertical deviation,the study of vertical deviation itself and its relationship with gravity anomaly,gravity disturbance and gravity gradient has gradually become a frontier of gravity measurement.This paper briefly introduces several methods of the deflection of the vertical,and the application method and problem solving of Geographic Lib based on EGM96 global gravity model are explained.Based on the global gravity field model of EGM96 and using the Geographic Lib database,the distribution of vertical deviations in north-south and east-west directions in three survey areas is calculated.The internal relations between vertical deviations and gravity disturbance,gravity anomaly and gravity vertical gradient are systematically analyzed.The Vening Meinesz formula and the Inverse Vening Meinesz formula are studied,and the vertical deviations in horizontal gravity are analyzed.In the distribution maps of values in the north-south and east-west directions,the influence of disturbance has been found to have obvious high and low value fast changing regions,and the location is consistent.Compared with the distribution of horizontal gravity disturbance and vertical gravity disturbance,the peak area of vertical gravity disturbance is usually the fast changing area of high and low values of horizontal gravity disturbance,which indicates the auxiliary delineation of horizontal gravity disturbance.There is consistency between high and low values in the fast changing area.Compared with the distribution of horizontal gravity disturbance and vertical gravity disturbance,the peak area of vertical gravity disturbance is usually the fast changing area of high and low values of horizontal gravity disturbance,which indicates the auxiliary delineation of horizontal gravity disturbance.The error relationship between gravity anomaly and vertical deviation is deduced.Comparing with the complex and simple relations of gravity vertical gradient,the causes of the three neglected terms are discussed in detail.The 2 ? value is too small,and the influence on the expression is too small within the accuracy range.It can be ignored that,2 ?comes from the transformation of Cartesian coordinate system and spherical orthogonal coordinate system.(69)? is related to the position of the calculated point,i.e.the parallel circle is a big circle or a small circle.The vertical gradient of gravity anomaly and vertical gravity disturbance are calculated and compared,and the distribution of the anomaly values is obviously consistent.Abnormal vertical gradient can reflect local anomalies more sensitively.