1. A method for determining a distance to an obstacle from a camera mounted to an automobile, the method comprising: tracking a plurality of features across two or more successive images; identifying off-ground features from the tracked plurality of features based on a ground motion estimate and respective motion of the plurality of features tracked across two or more successive images; and calculating for each off-ground feature of the plurality of features a distance to the camera based on motion of the feature in the images captured by the camera projected to a ground-plane and the ground motion estimate.