As previously mentioned, the optimum situation is to have the largest semi-circle possible but this of course is not always possible. In addition, this is highly dependent on having reliable individuals setting up the course which does not happen too often! This is why the measurer should be onsite and help to set up the course at major races.
A few thing to remember when creating/measuring a turn - around:
- you will need more room on the end side of the turn then the start side for the runners.
- When indicating the landmarks for the turn note both the cone line and the measured line which of course will be different by 0.30m. This difference can be significant in a race walk course.
I usually paint a dot for the center of the radius + a long arrow pointing to the outer edge of the cone line. I will also paint dashed lines for the cone placement