Comparison of Height Anomalies Determined from SLR, Absolute Gravimetry and GPS with High Frequency Borehole Data at Herstmonceux

The UK Space Geodesy Facility has operated a highly precise Satellite Laser Ranging station at Herstmonceux in southern England for over 25 years and the laser ranger is one of the ILRS core stations. It also operates two GNSS receivers contributing to IGS for over 14 years, and an Absolute Gravimeter (AG) which provides 24-h data weekly since November 2006. The facility has environmental monitoring in the form of a borehole, in close proximity to both the SLR and the gravimeter room, which provides automatic ground-water level measurements, and precise temperature, pressure and humidity devices. In this work we will investigate time series of site height variations determined by the independent techniques of SLR, AG and GPS since November 2006. The geodetic results suggest annual periodic vertical variations of amplitude about 15 mm and the absolute gravity values show systematic variations of order four microgals. We are particularly interested in the hydrological effects on the gravimeter data and will aim to use the space geodetic results to separate them from local vertical signals.