This paper describes an efficient method to obtain 3D information by using spatio-temporal analysis of omni images for outdoor navigation and map-making in the intelligent transportation system (ITS) application. Two types of omni-directional cameras are employed to make a spatio-temporal volume, which is a sequence of omni images stacked in the spatio-temporal space. For the spatio-temporal analysis of an omni image, we define several different cross sections in such spatio-temporal volumes, and examine characteristics of the traces of image features on the cross sections. We determine that the vertical straight lines in the real world are preserved as straight lines on these cross sections and that the degree of this slope represents the quotient of the velocity of the camera motion and the depth of the object. To acquire 3D information using these characteristics, we propose a hybrid method of the epipolar-plane image (EPI) analysis and the model-based analysis. To demonstrate the effectiveness of this method, we present some experimental results and the ITS applications using an omni-directional video camera to obtain images in outdoor environments.