International Gravimetric Connections along the Circum-Pacific Zone (III)

-Sensitivity Characteristics of LaCoste & Romberg Gravimeters (Model G) and Measuring Error Caused by the Setting Error of the Gravimeter (Supplementary Report)-

Abstract

This article is a supplementary report following the previous one on the sensitivity characteristics of LaCoste & Romberg gravimeters (model G) and deals with a measuring accuracy of gravity measurements performed throughout the whole period of international gravimetric connections which were carried out at selected cities mainly along the Circum-Pacific zone from 1979 to 1982. An optimal offset angle of the LaCoste & Romberg gravimeter (model G) was experimentally examined on the basis of theoretical considerations. It was ascertained that the optimal angle is variable not only with gravity value at each measuring station but also with zero-drift accompanied to the readout amplifier. The result of the examination revealed that the setting error of the gravimeter at each gravity measurement was small; namely, its amount due to the bubble drift was just cancelled by zero-drift of the readout amplifier. It was confirmed that the gravity measurements were performed with high accuracy; in other words, the measuring error caused by the setting errors of all gravimeters employed for the present investigations was less than 0.01 mgals usually and 0.02 mgals at maximum throughout the whole period of the investigations.