1. Geophysical Survey Center, China Geological Survey, Langfang 06500, China 2. School of Geophysics and Information Technology, China University of Geosciences (Beijing), Beijing 100083, China 3. Civil-Military Integrated Geological Survey Center, China Geological Survey, Chengdu 610000, China 4. Langfang Center for General Survey of Natural Resources, China Geological Survey, Langfang 065000, China
Gravity survey is an important part of geodetic mapping and geophysical exploration. Different gravity specifications adopt different methods to calculate the zero drift rates in two-way reciprocal observations (i,j,j',i'). The repeated measurements of point j are subjected to static drift in the geological survey specification. By contrast, the zero drift rate is calculated through regression analysis in the petroleum specification. Different processing methods for the repeated measurement interval of point j yield significantly different zero drift rates based on the two specifications. Through theoretical formula analysis and comparison of measured data, this study analyzed the influence of g'j- and t'j-tj in the repeated measurements of point j on the calculation of the zero drift rate. By comparing with the regression analysis, this study illustrated the importance of static drift in reducing the uncertainties caused by instrument performance and measurement environment. Moreover, this study proposed the applicable conditions of the two specifications.
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