Orthographic Projection > First angle

Learning outcome:

• I can recognise the direction of viewing used to derive the various views in first angle projection
• I can project the elevations of a simple solid in first angle projection

By the end of the lesson I will be able to:

• Draw a front elevation
• Draw an end elevation
• Draw a plan
• Draw the first angle symbol

Before studying this lesson I need to make sure that I know how to:

• Draw construction lines
• Label neatly in block letters
• Apply different line weights to construction lines and bold lines

Orthographic Projection

The orthographic projection is a way of drawing an object as seen from three different directions. To demonstrate this, we will use the simple object shown below, a video of which can be viewed at:

The three directions from which the object is to be drawn are shown below. They are called Front Elevation, End Elevation and Plan. This helps us distinguish between one view and the other.

In this other video the same object is shown with its surfaces colour coded. The surfaces that can be seen from the front elevation are coded in green, the ones seen from the end elevation are coded in blue and the ones seen from the plan view are coded in red.

When drawn in orthographic projection, this object is drawn as shown below.

Note that the views are neatly labelled so that we know what we are looking at. Also note that they are drawn aligned to each other. This is shown by the faint lines projected from one view to the other. The positioningof the views is also important. An easy way to know where you should place a view is by looking at its arrow in the three dimensional view of the object.

For example, the arrow of the front elevation is pointing to the top left hand corner of the paper.

This means that the front elevation should be drawn at the top left hand side of the paper. In the same way, since the arrow of the end elevation is pointing to the top right hand corner, the end elevation is to be drawn in the top right hand corner. The arrow for the plan is pointing directly downwards, but in the case of the plan, we do not draw it in the bottom centre area of the paper. Instead we draw the plan aligned to the front elevation.

The first angle symbol and its dimensions are given below.

Download PDF version (A4)