1. 1 Center for Measurement Standards(CMS)-National Measurement Laboratory(NML) (JohnLee@itri.org.tw)JohnLee@itri.org.tw 2 Department of Civil Engineering, National Chiao Tung University(NCTU), (hwang@geodesy.cv.nctu.edu.tw) 3 Ministry of the Interior (MOI), Taiwan (Hgf@gps.moi.gov.tw ) Results of Absolute Gravimeter Measurements in Taiwan Chiung-Wu Lee 1, Ge-Fu Hwang 2,3, Hui-Chin Yu 1, and Cheinway Hwang 2 ICAG Workshop 2005 19 Sep. 2005 BIPM, Paris

2. Abs. Gravimetry in Taiwan Using FG5 224

3. Results of observed gravity B12 at CMS Date 2003 2004 978913730.3 μGal Std. error: 3.4 μGal

4. Uncertainty Evaluation The expanded uncertainty U e = k c u c k c =2.0, 95% level of confidence, u c = 3.2 μμGal, U e = 2.0 × 3.2μGal = 6.4μGal

5. Abs. gravity survey( Ⅰ ) Taiwan

6. Summary of FG5 observations LocationTime span Mean gravity( μ Gal) Mean Standard error( μ Gal) Kenting 2004/2/5 – 2/6 (43 hours) 978790573.20.7 Mt. Yangming 2004/2/8 – 2/10 (63.5 hours) 978813961.80.6 Hsinchu 2004/2/11-2/12 (48 hours) 978913729.30.7

7. Comparison of NCTU and FG5 solid earth tide effects at Hsinchu

8. Comparison of NCTU and FG5 ocean loading effects at Hsinchu

9. Modeling solid earth tide and ocean loading effects

10. Land Subsidence Determination

11. summary of FG5 observations ( unit ： μ Gal )

12. Abs. gravity survey( Ⅱ ) Simultaneous and continuous gravity, GPS and sea level observations were made at Mazu, Kinmen, Penghu, Lanyu and Hsinchu for at least 3 days GPS, gravity and tide stations are either co-located or separated by a short distance Taiwan Mainland China

13. FG5 S/N 224 was used 50 drops a set, 30-minute set interval, 48 sets a day All environmental corrections, except ocean loading effect, were made The Sumatra earthquake occurred while measuring gravity at Lanyu Absolute gravity measurements

14. Date μGal Data of Lanyu

15. Amplitude and phase of M2 tide Observed 3.7 m,-31º 2.2 m, 58º 2.7 m, 7º 0.9 m,-2º 0.8 m,-133º The M2 wave propagates to China Seas from the Pacific Ocean Mainland China Taiwan

16. The amplitudes of M2 wave from gravity and GPS observation are larger than those from modeled results The characteristics of ocean loading effect along the southeast China coasts and Taiwan Strait are different from those in the Pacific Ocean east of Taiwan Amplitude and phase of M2 gravity Observed and Modeled

17. Joint MOI-Kyoto Measurement

18. Results from CMS and IAGB-KYOTO

19. Metrology

20. Superconducting Gravimeter

21. ICAG-2005 e_mail ： JohnLee@itri.org.tw Chinese Taipei Taiwan Thank You