One of Athletics Canada’s main roles in the road running community is to ensure that races are accurately measured. This is something very important to runners and race directors: how do I know I just ran 10k? How can I make sure my marathon course is really a marathon?
There is a two step process: first, the course is measured, and then, the course is certified. Measurement of a course is usually done on a bike, with a Jones Counter. The bike has to be calibrated depending on temperature, so measurers rely on calibration courses measured out with steel tape. The length of steel tape varies with temperature so a temperature adjustment using the coefficient of thermal expansion/contraction is made and the calibration course is adjusted for this temperature error. Once the calibration course is nailed off, there are two permanent markers that tell the measurer the beginning and the end of the usually 300m course. You can see the certificates for these courses in our database along side race courses.
Once the bike is calibrated, the course is ridden at least twice, with particular rules for going around corners and avoiding obstacles. The course should take the shortest line around turns. If something gets in the way, for example a tree or construction, the bike should be offset to one side, and the measurement can continue.
Once the course is measured, using the Jones Counter, several mathematical adjustments are made so that if there were any errors, they aren’t repeated over the entire course. This means that a course measured at 10k can be 10,010m +/- 10m maximum.
The next step is certification. The various mathematical calculations, mapped route and methodology is sent to Athletics Canada, where the numbers are checked to make sure they are accurate. While we can’t go out and re-measure all the courses, we do look for obvious errors and missed steps. Bernard Conway, an IAAF A-level measurer, has been Athletics Canada’s lead in this area for over 30 years. He checks and rechecks the work of the many course measurers throughout Canada.
A question that often gets asked is what about GPS? Runners participating in road races will often finish and their watch will tell them they ran 9.7k or 10.1k. Are these courses poorly measured? Probably not, if they have been measured by an AC measurer and certified by Bernie!
Conway tells us that since the advent of the GPS, it made sense to try to get the same level of accuracy using a variety of different gadgets. He told me that to get the same level of accuracy (+/- 10m on a 10k course) that the Jones Counter/bike/steel tape calibration method gets, they had to use a $40,000 military grade GPS! Your GPS just is not accurate enough to do it. This might make you think twice about relying on it for workouts, too…
The reason a GPS, especially a retail-level wrist-worn model, is not as accurate as the bike is that the GPS doesn’t measure your path as you run: it sends signals at various moments along the way to the satellite, every 1 to 20 seconds. In the time between signals, it assumes you have moved in a straight line between those two points. So you can imagine how not running in a straight line might play havoc with your device’s accuracy! As soon as you get rolling terrain, or buildings blocking the signal, errors start to multiply.
Since we can’t know when the errors are taking place, or how much of an error is made, there’s no way to calculate the margin. Here is an article that explains in much more detail the difference between the Jones Counter method and a GPS: http://www.riverregionrunners.org/html/gps_accuracy_article.html
So if you want to make sure you really have a PB in your latest race, check our database to find out if your race was measured and certified by Athletics Canada.