Vertical plane(VP) and Horizontal plane (HP) are generally used in orthographic projection. These planes of an object are obtained to describe it clearly with all dimensions. These are known as principle planes and the position of an object can be fixed by following four quadrants:

☛ (1) First Quadrant: It is above HP and in front of VP.

☛ (2) Second Quadrant: It is above HP and behind VP.

☛ (3) Third Quadrant: It is below HP and behind VP.

☛ (4) Fourth Quadrant: It is below HP and in front of VP.