Orthographic and isometric
Orthographic projection involves viewing an article being described in a technical drawing from different directions – from the front, from a side, from above, from below or from any other viewing position. Orthographic projection often involves: 1. The drawing of details which are hidden, using hidden detail lines. 2. Sectional views in which the article being drawn is imagined as being
cut through and the cut surface drawn. 3. Centre lines through arcs, circles, spheres and cylindrical shapes.