Any Two Monocular Cues

Shadowing lets us see the position of an object's shadow in relation to the object. Shadows can used to judge the distance from light and the size of the object. If a shadow is not attached to the object the object is not on the ground so we would not be able to tell the size of the object.

Motion Parallax is the tendency to think objects are closer to us when in motion seem to move faster than objects far away. This varies depending on the object's position and the observer's place of observation.