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3.3 Projection Systems

Multi view orthographic projection is the primary means of graphic communication used
in engineering work. Drawings are used to convey ideas, dimensions, shapes and

procedures for the manufacture of the object or construction of a system. The theory of

projection is the basis of background information necessary to shape representation in
graphics. Two fundamental methods of shape representation are used

• The orthographic view consists of a set of two or more separate views of an object

taken from the different directions, generally at right angles to each other and

arranged relative to each other in a definite way. Each of the views shows the shape

of the object for a particular view direction and collectively the view describes the
object completely

• Pictorial view, in which the object is oriented behind and projected upon a single

plane. Either oblique on perspective projection is used.

3.4 Orthographic Projection

The six principal views of an object or the glass box have previously been presented in the
type of orthographic projection known as Third Angle Projection. This form of projection

is primary form of projection found in all American industries while most other countries

use the other type of projection called First Angle Projection.

Figure 3.4 : First angle and third angle system