My understanding is that the accuracy of the GPS course will be pretty close to the wheel measured course unless the course has a lot of turns. theoretically, if the course is a straight line it should be accurate to within +-10 metres or so.

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Swimming Workout of the Day:

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2020 National Masters Champion - M50-54 - 50m Butterfly

The local race director here was demonstrating this to me just a week ago on the 8k running course he had just set up. He was showing me his original paint line for the finish from the GPS, and then where they ended up with Bernie Conway and a Jones Wheel certifying the course for records etc. The two marks were +/- 150 metres apart at the end of the 8k.

In his opinion, that was really bad that the gps was off by 150m compared to the certified distance. This was by the way out in the country in Grimsby, right next to Lake Ontario. There are no obstructions to the satellite signal.

When measuring curves on a run course is it the tangent that is measured?

That's what I suspected but wanted to be sure.

Thanks for the replies.

Cheers,

Steve


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Its my belief that with the Jones Wheel you must use tangents around corners, thus certifying that the most direct route is the official race distance. Anything longer is up to the individual racers - another reason why I always run the tangents (at least in races).

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Peter Solymosi
The Tri Bike Fit Studio
Vernon, BC

I criss cross the road and sometimes wonder why others don't.

Right--you measure the shortest distance possible that the runner can legally run the course. That way, you know that no one does less than the advertised distance unless they cheat.

The RD showed me the book, complete with diagrams of how to measure a wide variety of corners, depending on what sort of road closures and traffic controls are in place. Typically the shortest route is measured, providing it is safe to follow.

Yes, I think you can run slightly shorter than the measured distance because the official lines have to be a certain distance from the curbs...

I've used two different GPS systems (Garmin and Timex) and been wholly underwhelmed, the wheel seems way more accurate. With the older Timex GPS system I ran out a distance reported at exactly 5.00 miles, then retraced exactly, and it said I'd done 10.20. I consistently saw less extreme examples of the same. They're not good in areas with many trees. Using a wheel or a bike calibrated accurately on a track seems a lot better.

I also find the google-maps powered measuring tools such as
http://www.usatf.org/routes/map/ or http://www.mapmyrun.com
to be more accurate than GPS, provided that you use the satellite view, and not the map view.

At races I've heard people report distances for the same run that have differed by more than 1% when they measured the same distance. 1% might be fine for logging your runs, but not for measuring courses.

Cyclonehockey recently ran a 5K with a Garmin GPS and recorded 3.18 miles as the distance. So, you can expect (much like open water swimming) that you will zig and zag just a bit (or that the gps watch isn't super accurate).

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-----------------------------Baron Von Speedypants
-----------------------------RunTraining articles here:
http://forum.slowtwitch.com/...runtraining;#1612485

If want to get it right, you need a Jones-Oerth Counter.

Check out http://www.coursemeasurement.org.uk/ for a desciption and disscussion.

Jim

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James Meyer
Quarq Founder / SRAM