The Application Of FG5Absolute Gravimeter In Projects

FG5gravimeter is the most commercially successful absolute gravimeter in the world. Itscharacteristics are movable and accurate. As of2009, China has introduced a multiple FG5gravimeter, which have participated in the "2000China Gravity Basic Network","The CrustalMovement Observation Network of China","The Environment Monitoring Network of ChinaContinental Tectonic ","" XXX "Engineering" and "South Pole Research" and other majornational foundation engineering project. This article briefly describes basic measurement processand the basic principles of the FG5absolute gravimeter, focus on the problems existing in theapplication of FG5in "China tectonic environment monitoring network" and "" XXX" project"and analyzes how to correctly measure by FG5absolute gravity to improve the accuracy andreduce influence of tidal and earthquake on the result of the measurement.In the end, it studiesthe acceptance method of FG5data of base station and the basic law.The main work and innovation points are as follows:(1) This article summarize the FG5absolute gravimeter measurement rules, how to ues FG5instrument and G software and studies method of the FG5absolute gravimetermeasurement;(2) The FG5data acquisition and processing system are analysed. Basic principle of theabsolute gravity survey data processing is studied. This article summarizes thecorrection formula of the absolute gravity survey and calculates the influence of the poleshift correction on measuring accuracy;(3) The accuracy evaluation experiment is designed. By analyzing the accuracy of themeasured results for FG5absolute gravity meter/240determined, the FG5/240metersprecision is given which meet the requirement of the land state network;(4) The key technology of FG5absolute gravity measurement is studied. Through themeasurement and calculation, this paper puts forward instrument selection standard inthe gradient measurement;(5) The relationship between number of groups and precision is studied. According tocalculation of the actual data, it shows that the drop times can be set to100and12groups observation can meet the measurement accuracy requirement at inland point;With the influence of Marine load tide and the stability of the point foundation,16groups observation can meet the measurement accuracy requirement at offshore andisland point. (6) Three kinds of tidal correction model are studied. According to the actual calculationresults, it shows that difference of three kinds of tidal model correction value is large.No matter at inland, offshore or island point, fes2004and CSR tidal model diagramconforms to the observation result diagram better. At inland point, three kinds of tidalmodel correction curve are basic coincidence and the main reason is that the inlandpoint is far form see, so any tidal model correction is not large and do not affect theobservation accuracy.(7) The acceptance method of FG5absolute gravity survey to reference station is putforward. The reference station quality experience law based on the analysis of measureddata is given.1) When observation data standard deviation≤5mgal and group discretedegree amplitude <20mgal, reference station is bedrock point;2) when observationdata standard deviation>5mgal, group discrete degree amplitude <30mgal, referencestation is bedrock point;3) when observation data standard deviation>5mgal, groupdiscrete degree amplitude>100mgal, reference station is soft base.