Orthographic Projection

Chapter - 9

Orthographic Projection

At the end of this chapter we will be able to:

1. Define Orthographic Projection.

2. Define the terminologies used in orthographic projection.

3. Know the importance of multiview orthographic projection.

4. Differentiate First angle and Third angle orthographic projections.

5. Arrange the multiview orthographic projections in First angle and Third angle projections.

6. Understand the method of drawing orthographic projections in First angle projection.

7. Draw the multiview orthographic projections for the given three dimensional objects in First angle projection.

INTRODUCTION

It was explained in the previous chapter that projection is an image of an object as observed by the observer. Three major types of projections are (i) Perspective projection (ii) Oblique projection and (iii) Orthographic projection. In both perspective and oblique projections, the true shape of the object is not viewed since the projectors are not parallel to each other, observer is very close to the object and the projection represents all the three dimensions of the object. As all the three dimensions of an object is to be represented on a drawing sheet having two dimensions, (length and breadth), the true shape / size of the objects are not drawn in perspective and oblique projections. Hence orthographic projection is most commonly used since the true shape of the object is drawn and the projections are of two dimensions. Terminologies used in orthographic projection and the types of orthographic projections are explained in this chapter in detail.