Elements of descriptive geometry, with applications to isometric projection and othe forms of one-plane projection; a text-book for colleges and ingineering schools by O. E. Randall.

CHAPTER III

SUPPLEMENTARY PLANES OF PROJECTION
52. Supplementary Planes of Projection. While H and Vare the
principal planes of projection, projection may be made upon any
plane which we may choose for that purpose. Any plane other
than H or V which is used as a plane of projection is spoken of as
a supplementary plane of projection.
The most common supplementary plane of projection is a profile
plane of projection, - a plane perpendicular to both H and V and
consequently perpendicular to G-L.
53. Representation of the Point upon a Profile Plane of Projec

tion. In Fig. 34, which is a pictorial

Nm —
f~ I
Xi ii/P
[..[.o,~, P

7

~o r' ---- -l;
--- - - --

drawing, let the points
M, N, 0, and P have
the same location with
reference to Hand Vas
in Fig. 1, and let the
plane P represent a
profile plane of projection and situated to
the right of the given
points.
According to Section 5, the profile projection of M, or the
projection of M upon
P, is MP; the profile

0I,
o w -- -- --

FIG. 34
FIG. 34

projection of NV is NP; the profile projection of O is OP; and the
profile projection of P is PP.
Here it will be observed that the distance of the point itself
from V is equal to the distance of its profile projection from V,
and that the distance of the point itself from H is equal to the
distance of its profile projection from H.
24