How a Course is Measured
In a fascinating LetsRun.com article looking at how far exactly did Kipchoge run during his sub2 hour marathon attempt there was a section about course measuring.
This is very important subject for all runners who are looking to PR. The authors discussed if Kipchoge actually ran farther than a marathon and if that cost him the 1:59:59.
Below you'll see how a course is measured:
The first thing that Katz explained is that a course measurer is supposed to measure the shortest distance between two points on the course, cutting the tangents. So as long as the measurer does this and the runners stay on the course, they’re going to run at least the proper distance. On turns, like on a track with a rail, the measurer measures 30 centimeters from the curb. In theory, if a runner could hug every turn perfectly, they could shave off a little distance, but that doesn’t occur in reality. Katz said even for the 200m race on the track, where there is only one turn and the runners could try to hug it perfectly, he thinks the runners are running at least 200m.
Olympic Marathon Course Measurer
So you see, it's measured by the shortest possible route. So if you take wide turns during a race on a certified course, you're running farther than the course is measured! For the average half marathoner, doing even an extra .1 of a mile at a half marathon will add a minute to their time.
I consider taking the tangents to be the #2 most important piece of racing skill behind proper pacing.
How are certified race courses actually measured?!?