Maintenance of Millimeter-level Geodetic Reference Framework

The high-precision terrestrial reference frame, as the spatial benchmark for geodesy, is an important national infrastructure. However, due to the influence of nonlinear factors related to geophysical phenomena, the overall maintenance accuracy of the ITRF framework is still at the centimeter level. Therefore, accurately characterizing the true trajectories of linear motion, nonlinear motion, and geocentric motion of the reference station is the key to achieve the construction and maintenance technology of a millimeter level terrestrial reference framework. Based on long-term global and regional GNSS observation data, more Chinese geodesy scientists devoted much efforts to the maintenance of millimeter-level geodetic reference framework. The main contributions of this work included the followings: ①Dynamic maintenance of millimeter-level terrestrial reference frame;②Research progress on the method of maintenance of regional reference frame based on GNSS; ③The progress of CGCS2000 frame maintenance in millimeter level accuracy; ④Reprocessing and reanalysis of two-decade GNSS observation in continental China; ⑤Research on current GNSS velocity field model and deformation in Chinese mainland; ⑥The preliminary realization and evaluation of CTRF2020.