Lesson Notes By Weeks and Term v4 - JHS 3

Lesson Video

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Performance objectives

• Explain orthographic projection.
• Tell the difference between first and third angle projections.
• Draw simple objects using first angle projection.
• Draw simple objects using third angle projection.

Lesson summary

This lesson introduces one of the most important skills for any designer, engineer, or craftsperson: how to communicate a three-dimensional (3D) idea on a flat, two-dimensional (2D) piece of paper. Imagine you are a brilliant furniture designer in Accra and you want a carpenter in Kumasi to build your new chair design. How do you send them the exact instructions so they build it perfectly? You use orthographic projection. This is the universal language of technical drawing used by architects, builders, product designers, and artisans all over Ghana and the world. It allows us to show every side of an object with precise measurements, leaving no room for guesswork.

Lesson notes

A. What is Orthographic Projection?

The word "orthographic" comes from two Greek words: 'orthos' meaning straight or at a right angle, and 'graphos' meaning drawing.

Definition: Orthographic projection is a method of representing a 3D object in 2D. It shows the object from different viewpoints, typically the Front, Top, and Side views. The key rule is that you are always looking at the object *straight on* (at a 90° angle) from each side. This means there is no perspective; lines that are parallel on the object are drawn parallel on the paper.

B. The Principal Views