Advances in Dynamic Maintenance Technology of mm-Level Terrestrial Reference Frame

The mm-level dynamic maintenance technology is essential to the realization of mm-level terrestrial reference frames. The current dynamic maintenance technology mainly includes the linear maintenance based on linear velocity, the nonlinear maintenance technology that comprehensively considers the nonlinear motion of stations and geocentric motion, and the epoch reference frame. Firstly, the development status of the linear maintenance technology is summarized. The nonlinear maintenance technology and its research progress are discussed by reviewing the modelling method of coordinate nonlinear variation from the influence mechanism and data. Then, the realization process of the epoch reference frame and its application in the maintenance of the reference frames are introduced. Finally, based on the analysis of status quo, several key issues that need to be solved are proposed to achieve the dynamic maintenance of the mm-level terrestrial reference frame.