The Course Was Long!

Before you accuse the race director of measuring his course long, please do your research.

You just finished the marathon and your Garmin says you ran farther than 42.2k or 26.2 miles. Worse still, you missed your Boston Qualifier by a couple of minutes and you are pretty sure you could cover that extra 400 or 500 metres in less time than that. But they said the course was certified?

Before you send a nasty email to the race director, rant about it on Twitter and slam the race on your blog, ask yourself a few questions:

  • How many kids did I high-five along the side of the road?
  • How many other runners did I pass?
  • How many walkers did I have to dodge?
  • How much did I weave through water stations to get just the right flavour of Gatorade?
  • How often was I completely alone running the straightest possible line and taking the shortest, most direct route through every turn?

Unless you answered ‘the entire race’ to the last question and ran the tangents perfectly, any deviation from the shortest line between A and B will add metres to your total, and those high-fives and second helpings of Gatorade can add up. (If you answered ‘none’ to all the other questions, ask yourself if you had any fun.)

My fancy new Garmin is 100% accurate isn’t it? No really, isn’t it? As great as they are, the fact is that even if you paid $500 for yours, GPS-based sports watches aren’t 100% accurate.

If you’re still convinced the course is long, please read The Measurement of Road Race Courses, the IAAF’s official word on course measurement available on Athletics Canada’s Course Measurement site. The document offers more information about course measurement than a casual marathoner could ever need and illustrates how difficult it is to run exactly 42.2 kilometres on a certified course, particularly for a mid-pack runner who is constantly surrounded by other runners and can’t run the shortest possible route.

It also includes the following note:

To prevent a course from being found to be short on future re-measurement, it is recommended that a “short course prevention factor” be built in when laying out the course. For bicycle measurements this factor should be 0.1% which means that each km on the course will have a “measured length” of 1001m.

It’s not only difficult to run a 42.2k certified marathon, it’s technically impossible since the course, in order to be certified, should actually be 42.24 kilometres.

There are long courses — last year’s BMO Vancouver Marathon for example, though it was long because of misplaced cones, not a mismeasured route — but unless it’s REALLY over, don’t blame the race director. A lot of runners jump to the conclusion that if their Garmins say a marathon was a metre longer than 42.2 kilometres that the course is long. The bottom line is that GPS technology isn’t 100% accurate and with all the factors working against runners trying to get through a marathon as quickly as possible, if you can cover a course less than 1% over, pat yourself on the back.


  1. My Garmin said 42.45 km for BMO on Sunday. I find that the accuracy is usually within 1% and for training runs about 0.5%. Yes, running the tangents is the main factor, but also weather, latitude and time of day can play a role for GPS accuracy. BTW, I remember that all major city races in Germany would paint a blue line on the pavement that outlined the shortest distance. The competitive runners would always gravitate towards this line. That was back in the eighties. Don’t know if they still do that, but it was pretty helpful.

  2. Mine showed a little longer than that but running as the 3:45 pace bunny I was weaving around a lot more, high-fiving kids, etc. so I wasn’t surprised. Last year’s Vancouver Marathon race director had painted a blue line which you can still see in some places (like turn onto Camosun).

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