What is the difference and similiaritties between an isometric drawing and an orthographic drawing? explain.

In orthographic drawing the three "dimensions" of an object are depicted in three views, each showing the object from one of three perpendicular planes. 
An Isometric drawing is a quasi 3d drawing that shows the height width and depth of the object in a single view where the viewpoint is at a 45 degree angle from each of the perpendicular planes of the orthographic view. 
Isometric differs from a perspective view in that all lengths are shown true length. In a perspective drawing the objects that are depicted to be more distant are shortened to make the view more realistic looking.

The best estimate would be about 1 foot