Overlapping projection views create confusion in the drawing. Therefore the 2nd angle projection system is not used to draw engineering drawings. Similarly when the object is placed in the 4th quadrant both top and front view will overlap. Therefore fourth angle projection is also not used.

The optimum take-off angle for a world-class long jumper may be anywhere from 15° to 27°. Linthorne, N.P. Optimum angles of projection in the throws and jumps.

Third angle projection is one of the methods of orthographic projection used in technical drawing and normally comprises the three views (perspectives): front, top and side.

Draw the grid in isometric using a 30 degree set square, being careful to use the same measurements as the original grid which surrounds the circle. 4. To draw the circle in isometric projection simply measure each distance down each vertical line on the normal grid and transfer it to the isometric grid.

1 : of, relating to, or characterized by equality of measure especially : relating to or being a crystallographic system characterized by three equal axes at right angles.

The isometric drawing is drawn using 100% true length measurements on the height, width, and depth axes. However, in isometric projections the height, width and depth are displayed at 82% of their true length. In isometric projections the object is first rotated about the Y axis by -45 degrees.

Isometric drawings are commonly used in technical drawing to show an item in 3D on a 2D page. Isometric drawings, sometimes called isometric projections, are a good way of showing measurements and how components fit together. Unlike perspective drawings, they don’t get smaller as the lines go into the distance.

Examples of drawing isometric drawing

• 1) Draw isometric drawing of a cube. Orthographic projection of cube of 40cm length, 40cm height and 40cm width is shown below.
• 2) Draw a square in isometric Square ABCD is of 50mm size. 1) Draw a horizontal line.
• 3) Draw an isometric circle.