92 Chapter 5
Comparison of Isometric and Orthographic Drawings.
Compare the simple rectangular block shown in the orthographic representation (third-angle projection)
in Figure 5.18 and the three-dimensional isometric representation. Notice that the vertical lines of the or-
thographic and isometric drawings (views A and B) remain vertical. The horizontal lines of the ortho-
graphic drawing are not horizontal in the isometric drawing but are projected at 30- and 60-degree an-
gles; the length of the lines remains the same in the isometric and in the orthographic drawings.
Figure 5.17B An example of the use of isometric drawings in architecture and engineering.