Abstract:
Traditionally, gravity measurements were observed by using conventional methods
such as pendulum. Later, it was developed to various instruments including remote
sensing techniques. CG-6 Autograv Gravity meter is an automated gravity meter that
has a worldwide measurement range of over 8,000 mGals and a reading resolution
of 0.0001mGal. This enables the user to operate in both detailed micro-gravity
surveys and large scale regional or geodetic surveyors. Rain, wind and other
meteorological variations directly impact the gravity measurements. Further, these
gravity measurements employed various correction models such as temperature, tilt,
tide, drift for reduce other influences. Gravity measurements taken near the sea could
be directly affected by daily tidal changes. The aim of this study was to determine
the effect of tides on gravity measurements and to eliminate the tidal effect from the
gravity measurements. Gravity data were obtained from the CG-6 auto gravity meter
at Colombo Port and Sabaragamuwa University continuously for 25 hours. Tidal
data at the Colombo port were also collected simultaneously with the gravity data.
Since the university is situated at inland area, there was no effect due to the tide
observed. This data were used to validate the tidal effect. Bougueranormaly
correction was used for eliminate the tidal effect from the gravity measurements by
computing the mass variation due to tide. Finally, after correcting for the drift
correction, a good correlation between observed gravity measurements and mass
variations due to tidal fluctuations was observed.
