depths of receding surfaces definition

 The depth of a receding surface refers to the z-axis of an object, as opposed to the object’s x-axis or y-axis, ( its width and height).  There are two main ways to discover the depth of a recediing surface.  One way is to use diagonal lines with a scale that recedes.  The second way is through the use of a scale on the base-line or parallel to it.  The first method is often used to free-hand sketch things such as a foreshortened row of fence posts.