Abstract: Direct positioning and data acquisition system,composed of global positioning system(GPS),inertial navigation system(INS),laser ranging technique and digital photogrammetry,is a fast data acquiring technique developed in recent years.And the vehicle-borne 3D data acquisition system based on this technique is paid attention by more and more people.The direct positioning equation,which can directly work out 3D coordinates of pixel is presented.Roderick matrix is used in absolute calibration of the system to work out shift and rotation parameters,indispensable for the equation,between camera and INS-carrier coordinates datums.Then formulas for errors of 3D coordinates and point location are deduced according to the error propagation law.The experimental results show that proposed calibration method has clear physical meaning,simple calculating process and high precision.