Calibration of outdoor cameras from cast shadows

We introduce several efficient methods for automatically determining the absolute (Earth-relative) orientation and intrinsic lens parameters of a stationary, fixed-field-of-view outdoor surveillance camera. Our approach uses shadows observed over time to produce absolute world-to-camera correspondences. We demonstrate how projective features may be derived from shadows cast by stationary or moving objects in the scene, and how the resulting geometric relationships reduce the problem to classical camera calibration.