A projection will be recognized as the first angle projection, whether the object to be projected is considered to be located in the first dihedral angle or the first quadrant. Its position will be defined like in front of the vertical plan as well as above the horizontal plane.
The projection will be termed like the second angle projection whenever the object is considered in the second quadrant. Its position will be behind the vertical plane and above the horizontal plane. The planes are seemed to be transparent, thin and dimensionless. The horizontal plane is expected to be hinged about the line of intersection along with the vertical plane.
Imagine a point P located in the first quadrant in diagram is the edge-wise view of the reference planes that is HP and VP. Its co-ordinates are x-y. From P, a projector is sketched to the vertical plane. It will generate an image p′ on the VP. The distance of p′ from the line of intersection that is from X-Y line will be y units from P another projector is sketched perpendicular to horizontal plane. It will generate an image on the horizontal plane at x units away from the origin.