STUDY ON STABILITY OF GNSS OBSERVATION MARKS USING
VERTICAL PENDULUM TILTMETER
1)Key Laboratory of Earthquake Geodesy,Institute of Seismology，CEA，Wuhan 430071
2)Wuhan Base of Institute of Crustal Dynamics,CEA,Wuhan 430071
3)Shanghai Aircraft Manufacturing Co.,Ltd,Shanghai 200436
Abstract The tests analyzing the influence of meteorological factors on the stability of bedrock observation marks were taken for GNSS observation pillars in Huangmei and Jingmen to researchby using vertical pendulum tiltmeter.The result indicates that a regression daily offset movement of the pillars in SN direction and EW direction，and a bigger offset in SN over EW direction.The maximum amplitude of the daily offsets and the daily average offsets of the pillars in SN direction is within 3 mm and 1 mm，respectively，within 2 mm and 0.2 mm in EW direction，and the influence of change of seasons on amplitude is not obvious.The main reason of the offset movements of the pillars is the changes of temperature difference caused by the sunshine.Also，there is no significant relationship between the stability of the observation marks and rainfall，air pressure，and solid tide.The influence of daily offset movement of the bedrock pillars on the highprecision observation reminds us to take temperature protection against the pillars，or to make pillars of the materils with lower thermal expansion rate.
