Establishment of Absolute Gravity Datum in CMONOC and Its Application

The high accuracy absolute gravity datum covered the Chinese mainland area is established by using absolute gravity measurement data of one hundred stations in CMONOC (Crustal Movement Observation Network of China),the accuracy of each station is better than 5.0μGal/a .The high accuracy gravity datum can be used for relative gravity measurements in adjustment,and the real gravity value can be determined from relative gravity measurement data of adjustment by using the gravity datum to avoid distortion of the real figure of gravity change.The trend of absolute gravity change from several observations at Chengdu station shows that the secular trend of gravity change is larger than 5.01 ±0.7μGal/a ,which is probably caused by the distribution of mass below the earth.The rate of land subsidence of Wuhan area is 3.27±0.65 mm/a determined from combined long-term absolute gravity measurements and GRACE satellite data according to the two system difference.