1. A method for constructing a three-dimensional model of a scene captured as a video stream, comprising: obtaining a video stream of a scene by a first camera; locating a horizon with respect to the scene with a second camera, wherein the horizon is located as a function of a downward tilt angle of the first camera and a roll angle about a line of sight of the first camera; and in a processor in communication with a memory having instructions stored therein which, when executed, constructing a three-dimensional model of the scene based upon the obtained video stream and the located horizon.