Study On Datum For Normal Gravity Correction

The important purpose of gravity exploration is inspecting the Earth structure, thecrust structure and prospect for mineral reserves. The basic gravity observation includestwo parts: normal gravity and gravity anomaly. We subtract the normal gravity from thebasic observation to get the gravity anomaly，which can provide us abundant geologicstructure information. So it is important that gravity exploration must provide the gravityanomaly data with high accuracy.Gravity exploration and data pre-processing are closely related to the datum. Andthe change of the datum which can help to express the planimetric position and elevation(or geodetic height) may make an impact to the result of gravity prospecting and datapre-processing. That is to say, choice of coordinate systems and reference ellipsoids forEarth has a direct influence on accuracy and rationality of gravity external correction. Soit is important to study on the datum of normal gravity correction.Through surveying the relevant datum and the method of normal gravity calculation,we study the effect on normal gravity correction caused by different reference systems.Also by analysing the process of normal gravity calculation, we make it clear that thedatum of normal gravity correction is ellipsoid, not geoid, This work increases theaccuracy of gravity anomaly, and it provide gravity anomalies with high precision fordeducing the Earth’s inner structure, which is beneficial to the study of the Earth to betterserve human society.