How is distance in open water events measured?

I'm sure this has been asked before many times, but being relatively new to the sport, I was just curious to know. I did two triathlons this year: the first one my time was about 26 minutes, the second about 27 minutes - and the timing mat was immediately after the lake exit on both points.

Now of course I could have got slower, but assuming my fitness / peformance was more or less similar, the only other variable is the length of the swim. 

So how are these things measured - and is there an official accuracy - i.e. plus/minus 5 % ?

 

 

Comments

  • GPS maybe? 

    I know my local lake row it with a GPS so it's as accurate as the GPS itself is

  • A minute isn't that much to worry about.  A slightly worse start, going off course a little bit, weather they could all have affected you to give that minute. If it was 10 minutes I'd question it but not only a minute.

  • sketchily - in my humble experience.

  • Some Ironman races have impressively fast times, and some have slow times.  I dont think the distance is particularly accurate - but then again - not many of us swim the exact route !

    http://app.strava.com/swims/11899921 has a 2.4 mile swim as 2.9 miles for example.

  • If they do it properly then they use a GPS to position the buoys.  However, if the stretch of water is tidal then the buoys will move as the water level drops and the buoys have more slack in the rope.  Also buoys can be swept away by bad weather and currents, although this tends to be over a period of months rather than days and most good courses are laid out (or at least checked) close to the event.

    I can't remember what the accuracy of the course is, but it is supposed to be as accurate as the bike or run legs.

  • on cougies link its the up hills that give you the extra distance, i always prefer downhill  = loads quickerimage

  • never seen the bloke with the wheel measuring device walking on water, but would be impressed if i did!

  •  
    happy9053 wrote (see)

    never seen the bloke with the wheel measuring device walking on water, but would be impressed if i did!

    Thats because they do it under water wearing a diving suit image

    They have to measure the lake / sea bed as the wobblyness of the water surface would make it near impossible.

  • Bouncing Barlist wrote (see)
     
    happy9053 wrote (see)
    never seen the bloke with the wheel measuring device walking on water, but would be impressed if i did!

    Thats because they do it under water wearing a diving suit image

    They have to measure the lake / sea bed as the wobblyness of the water surface would make it near impossible.

    If you look in the BTF Rules you'll see this is clearly stated.

     


     

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