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4 PLANE INTO SYSTEM OF COORDINATE PLANES
4.1 REPRESENTATION OF THE PLANE

A plane of unlimited extent can be represented on a complex drawing by the projection of
three points which are not laying on one straight line; projections of a straight line and the point
which is not laying on the given straight line; projections of two parallel straight lines; two crossed
straight lines (Fig. 4.1).

Figure 4.1

In practice, these points are usually joined to form two intersecting lines or triangle, the latter
being a convenient form for graphical purposes.
A plane can be uniquely represented by its intersections with the coordinate planes (Fig. 4.2).

Figure 4.2

4.2 TRACES OF THE PLANE

Lines of crossing of a plane with planes of projections are called the traces of the plane (Fig.
4.3).
These lines of intersection of the plane with horizontal Π 1, frontal Π 2 and profile Π 3 planes of
projection are called, respectively, the horizontal, frontal and profile traces of the given plane. The
horizontal, frontal and profile traces of the plane Ω are designate, respectively, Ω 1, Ω 2, and Ω 3 or
h 0, f 0 and p 0 (Fig. 4.3).

Figure 4.3

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