1. A geo-registration method comprising: obtaining digital image data of an image source using a camera located a distance D from a center field of view (CFOV) of the image source, where f is the focal length of a lens of the camera and D>>f; obtaining inertial navigation system (INS) data of the camera associated with the digital image data, said INS data including camera position data and camera attitude data including roll (α roll ), pitch (α pitch ), and heading (α heading ); loading the digital image data into a graphics processing unit (GPU) of a computer system to be processed thereby; in the GPU of the computer system: calculating relative angles and distances between the camera and the image source from said INS data; performing geometry correction of the digital image data using the calculated relative angles and distances; performing geo-rectification of the geometrically corrected digital image data using an affine homogenous coordinate transformation, to produce a geo-rectified digital image data; performing heading adjustment by performing a rotation transformation about a z-axis of the geo-rectified digital image data to remove the α heading ; and performing geo-registration with the heading-adjusted and geo-rectified digital image data.