Last edited 09 Sep 2020

Drawing projections

There are a number of techniques of projection that can be used to represent three-dimensional objects in two-dimensions by 'projecting' their image onto a planar surface.

Drawing projections should comply with relevant standards (such as British Standards) to prevent misunderstanding and avoid errors in interpreting the drawing.

1 Orthographic projection
2 Axonometric projection
3 Isometric projection
4 Oblique projection
5 Parallel projection
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[edit] Orthographic projection

Orthographic projection is a type of 'parallel' projection in which the four orthogonal views of an object are shown. The orthographic projection commonly used in the UK is called first angle projection.

[edit] Axonometric projection

Axonometric projection creates a true plan set at 45º, which retains the original orthogonal geometry of the plan. It is particularly suitable for representing interior designs, such as kitchen layouts. Planning drawings can also be effective represented as axonometric projections, showing the relationships between buildings and topography.

The axonometric method became increasingly popular in the 20th century as a formal presentation technique, but recently has become less widely used due to the emergence of CAD programmes and building information modelling.

NB Drawing for Understanding, Creating Interpretive Drawings of Historic Buildings, published by Historic England in 2016 suggests that axonometric projection: 'Is a type of parallel projection used for creating a drawing where the plan is drawn to scale but rotated at an angle of 60° or 30°along one or more of its axes relative to the normal axis.'

[edit] Isometric projection

The isometric was the standard view until the mid-20th century. Unlike the axonometric projection, the isometric plan view is slightly distorted, using a plan grid at 30º from the horizontal in both directions. It can be used to show the nature of the design and explain construction details more clearly than an orthographic projection. It is sometimes used during concept design to help the client grasp the mass of the proposal.

[edit] Oblique projection

When primary information is drawn in elevation, the interpretation can be enhanced by an oblique projection. This is a simple method of producing two-dimensional images of three-dimensional objects. The differentiating characteristic of oblique projection is that the drawn objects are not in perspective, and so do not correspond to any actual obtainable view.