Reply to "addition to measurement at turning point"

Here is a way to add a turn-around point for 800 meters addition to the course:

1) Find a side road that is long enough.
2) Make a mark just before the side road. Call it point “A.”
3) Lay out 400 meters from point “A” to point “C.” Mark “C” temporarily.
4) Lay out 400 meters from “C” to a new point “B.”
5) Measure the distance from “B” to “A”
6) Add half of “B to A” to temporary mark “C.” This will be your turn around point.