1. Isometric Circle using the Ordinate Method
Drawing Abilities Teacher
Isometric Circle using the Ordinate Method
© J Lewis 2004

2. Drawing the Orthographic Circle
Draw a circle to a required diameter with centre lines A – A and B - B
© J Lewis 2004

3. Dividing up the Diameter
Divide the diameter A – A into a suitable number of equally spaced parts ( 8 in this example )
© J Lewis 2004

4. Drawing Ordinates
Number the points as shown and draw Ordinates ( Verticals ) parallel to B – B through these points.
© J Lewis 2004

5. Drawing the Isometric Square
Draw an Isometric Square with each side the same size as the diameter of the circle.
Draw A – A and B – B as the horizontal and vertical centre lines.
© J Lewis 2004

6. Drawing Ordinates
Divide the horizontal centre line into the same number of spaces as you previously did for the circle.
© J Lewis 2004

7. Drawing Ordinates
Draw Ordinates ( Verticals ) through the points on the centre line and number as shown.
© J Lewis 2004

8. Transferring measurements
The length of each ordinate, above and below the centre line A – A, is transferred from the circle to the isometric square.
© J Lewis 2004

9. Completing the Isometric Circle
The points at the ends of these lengths are then joined by a smooth curve to form the isometric circle.
Notice that the centre line B – B could also have been used to generate the circle ordinates.
In using this method, a few accurate ordinates are better than many drawn inaccurately.
© J Lewis 2004