A contribution to precision microgravity data analysis using LaCoste and Romberg gravity meters

The precision quoted for published microgravity surveys varies widely. This paper attempts to quantify the sources of error on a single gravity difference measurement using LaCoste and Romberg instruments. A combination of external effects (Earth tides, noise), reader effects (technique and field practice) and instrumental effects (tares, thermal drift, calibration) are shown to produce a maximum (worst case) error, for a single reading, of approx. 23 pgal and a minimum (best case) error of approx. 7pgal. Single difference measurements have corresponding errors of approx. 33 and lopgal, respectively. Evidence is presented to demonstrate the importance of thermal and mechanical tares which are best removed from field data by isolating step functions using repeat readings rather than by (always) assuming linear drift. Key words: LaCoste and Romberg gravity meters, microgravit