Many vendors allow users to produce the imagery with the pixel coordinate system rotated with respect to the direction of flight, and this is where things can get messy.
There are many ways for companies to mount their cameras in their aircraft which means that the pixel coordinate system is not always directly in line with the direction of flight. Sometimes users end up making a best guess, and will attempt to overcome improperly defined camera parameters, by adjusting the kappa value of the exterior orientation (EO) parameters. This can lead to unexpected behavior in applications further down the process chain, and can lead to inaccuracies. This is especially true if a Principal Point of Autocollimation (PPAC) needs to be applied. In this paper we’ll attempt to explain how to properly determine these parameters for use within the ImageStation photogrammetric application environment. Please see attached for the full discussion: