We demonstrate an efficient method to determine gravity field model using data from accelerometer- and GPS-equipped satellites, such as CHAMP. On the basis of the conservation of energy principle, in situ (on-orbit) and along track disturbing potential observables were computed using 16-days of CHAMP data. The global disturbing potential observables were then used to determine a 50 ¿ 50 test gravity field solution (OSU02A) by employing a computationally efficient inversion technique based on conjugate gradient <Han et al., 2002>. An evaluation of the model using independent GPS/leveling heights and Arctic gravity data, and comparisons with existing gravity models, EGM96 and GRIM5C1, and new models, EIGEN1S and TEG4 which include CHAMP data, indicate that OSU02A is commensurate in geoid accuracy and, like other new models, it yields some improvement (10% better fit) in the polar region at wavelengths longer than 800 km.