Angle projection:

Now for getting these projections of P, on a single plane surface, it is obligatory to rotate the horizontal plane clockwise like as in displayed diagram till it coincides along with the vertical plane. The portion of the horizontal plane such is in the first quadrant will go down and coincide along with the vertical plane below the intersection line X-Y, and the portion of the horizontal plane that is in second quadrant will rotate clockwise and coincide along with the vertical plane, above the reference line XY. Whenever we look at the whole arrangement perpendicular to the planes, it will appear as displayed in diagram (a) and (b).

It may be noted such the projections of point p are lying upon the similar projector that is perpendicular to the reference line XY. The projection of point p on the vertical plane, that is called elevation or front view is generally marked along with lower case letter p′, is of y units above X-Y line and the projection of P upon the horizontal plane is termed as Plan or Top view and is generally marked along with lower case letter p or without dash, is x units below the reference line X-Y.

Whenever the object is considered in second quadrant, its front view will be above XY line and the top view obtained on the horizontal plane will cover the front view. The horizontal plane is rotated clockwise only. Just imagine a drawing in that one view overlaps the other so the top view overlaps the front view. In this case, no details can be read. In practice therefore, there cannot exists the second angle method of projection.

Whenever the object is considered in the third quadrant as displayed in diagram (a), its front view will be under X-Y line and the top view will be above X-Y line. This is named the third angle method of projection.

And when the object is seemed in the fourth quadrant, the front view will be under the X-Y line and the top view will cover the front view. In practice therefore, the fourth angle projection method does not exist.