## Isometric Drawing and Isometric Projection

The term "isometric" is derived from the Greek for "equal measure," reflecting that the scale along each axis of the projection is the same, which is not true of some other forms of graphical projection. One of the advantages of isometric perspective in engineering drawings is that 60-degree angles are easy to construct using only a compass and straightedge.

The isometric drawing is most commonly used in its true form giving "equal measure" and foreshortened views of three sides of the object. An isometric drawing is one form of pictorial drawing. Hidden lines are not normally inserted. Isometric drawing is a method of visually representing three-dimensional objects in two dimensions, in which the three coordinate axes appear equally foreshortened and the angles between any two of them are 120 degrees. Isometric projection, like orthographic projection. is used in engineering drawings. An isometric drawing can be easily constructed by using a 30-60-90-degree triangle and T-square or with CAD programming. Figure 5.17A and B shows two examples of isometric drawings in an architectural context. Figure 5.17C gives an example of an architectural drawing using both orthographic projection (elevation) and isometric projection (details).

### ISOMETRIC DIMETRIC TRIMETRIC PERSPECTIVE

Figure 5.16 Different types of axonometric projections (isometric, dimetric, and trimetric) and perspective. In much of Europe, an axonometric uses a 45-degree angle as opposed to the 30/60-degree angles used in isometric drawing.

### ISOMETRIC DIMETRIC TRIMETRIC PERSPECTIVE

Figure 5.16 Different types of axonometric projections (isometric, dimetric, and trimetric) and perspective. In much of Europe, an axonometric uses a 45-degree angle as opposed to the 30/60-degree angles used in isometric drawing.

Figure 5.17A An example of the use of isometric drawings in architecture and engineering (source: North American Steel Framing Alliance).