Abstract

Using only shadow trajectories of stationary objects in a scene, we demonstrate that using a set of six or more photographs are sufficient to ac- curately calibrate the camera. Moreover, we present a novel application where, using only three points from the shadow trajectory of the objects, one can ac- curately determine the geo-location of the camera, up to a longitude ambiguity, and also the date of image acquisition without using any GPS or other special instruments. We refer to this as “geo-temporal localization”. We consider possi- ble cases where ambiguities can be removed if additional information is avail- able. Our method does not require any knowledge of the date or the time when the pictures are taken, and geo-temporal information is recovered directly from the images. We demonstrate the accuracy of our technique for both steps of cali- bration and geo-temporal localization using synthetic and real data.