Abstract: The digital zenith camera combining GPS and CCD techniques can be used to rapidly and precisely measure the vertical deflection based on the astrogeodetic theory.Basic framework of digital zenith camera is given.Algorithms to calculate the vertical deflection from GPS measurement and CCD star images are shown.Errors of vertical deflection measured with digital zenith camera are analyzed by considering the instrumental structure and observing procedure.The automation to measure the veritical deflection and the result precision with the digital zenith camera are better than those with the traditional astrogeodetic technique.