Absolute Gravity Measurement at KRISS

Abstract

Acceleration due to gravity is essential in the field of measurement and calibration of mass related quantities such as force, pressure, hardness, and so on. Applications of gravity are becoming more important in mineral resource exploration, geography, environmental monitoring, etc. Most gravity measurements in Korea are being carried out by using a relative gravimeter. The reliability of the measurements made by using relative gravimeters should be calibrated periodically at different absolute gravity points. However, Korea Research Institute of Standards and Science (KRISS) had only one absolute gravity point measured by the Chinese National Metrology Institute in 1996, and the gravity value was not measured or evaluated again until 2007. KRISS established an absolute gravity standard facility using the free-fall gravimeter principle equipped with an iodine-stabilized He-Ne laser and a Rb clock for the first time in Korea in order to make a reliable gravity calibration chain. The Korean gravity standard is now traceable to fundamental SI units of Korean time and length standards. A gravity difference of approximately 22 μGal at the old absolute gravity site has been detected by precise measurements and evaluation. The absolute gravity points established in Korea can be used for reference data and for the calibration of relative gravimeters.