Availability of accurate spaceborne gravimetry/gradiometry sensors and advances of extremely accurate clocks with stability at the 10^-18 level, enables the development of gravity field models at unprecedented resolution and accuracy, and geopotential difference determination employing relativistic geodesy. The purpose of this session is to solicit papers including but not limited to: (1) novel mathematical techniques leading to ultra-high degree global and regional gravity field/geoid determination, including optimal basis function representations and the corresponding modeling; (2) determination of local and global geoids towards improving the unification of the world’s height datum system; and (3) determination of gravitational potential differences based on relativistic geodesy, including precise clock transportation, gravity red shift, and recent developments in clock and time-frequency science.