General Theory on Heights and DistancesAngle of elevation: If the object is above the horizontal level of the eyes i.e. if it is above the eye level), we have to turn our head upwards to vie the object. In this process, our eyes move through an angle. Such an angle is called the angle of elevation of the object from our eyes.
Angle of depression: Suppose a boy, standing on the roof of a building, observes a ball lying on the ground at some distance form the building. In this case, he has to move his head downwards to view the ball. In this process, his eyes again move through an angle. Such an angle is called the angle of depression of the object from the location of his eyes (figure.)