Just to play devils advocate. People here will know better than me but to get a marathon accurate presumably you measure the bulk of the course then move the start/finish a bit to get it right. The exact distance will be the blue line route and, I guess, you choose barriers and such like so that there are no corners to casually cut. With most marathons, again I'm guessing, you are more likely to want the finish somewhere very specific so the give and take bit is more likely to be at the start?

With a Triathlon don't you have less room to play with the start of the run because of T2? If so maybe you could say any extra run is still transition and then the accurate marathon begins at a designated matt/line. But then aren't you just getting a longer run with an arbitrary line rather than a more accurate run? Would most people be happier with that? People who miss cut offs/pbs because of the extra run. Maybe you just have a 180 turn somewhere up and back a side road to get the distance right? Also maybe there are other parameters like drop and surface that would be required that would take some of the flexibility out of the run route? Just thinking out loud if it would be as simple as we're making it out to be.

Am I making sense? TLDR It seems it would be hard to get T2 and the desired finish line to be exactly marathon distance since the fixed nature of both doesn't gibe you much to play with.

I'm not sure what standards ironman uses for for course measuring, but I know that for ITU it's basically the same standards as for IAAF, except that there's no requirement for bringing in a course certifier to verify the course, which is what you need to do if you're looking to become a BQ.

You measure (with a calibrated wheel) 30cm off the shortest line throughout the course. The old school method was wheel the course start to finish, and then if you were off, you moved the start/finish lines to make up the distance. The new school method is to break the course into sectors, wheel each of the sectors, and do the math. You may also wheel off some additional alternate routing in case for whatever reason you need to make a change to the route, or you need to adjust the distances. out and back sections are often the easiest to make adjustments to, by moving the turn around a few meters to dial in the distance... The one unique bit in Tri, is that you essentially measure the course itself, but also have to measure from the run exit to entering the course proper as well as when the exit the course proper (for multi-loop) to head into the finish. You also generally wheel each sector multiple times to confirm the distances... When you're dealing with rougher surfaces, typically you move slower and/or you use a different wheel. In terms of elevation loss/gain, that does not factor into course measurement.... 1km is 1km, whether it's on a flat, uphill or downhill... That being said, for the sake of Boston, they could set max specs in terms of net elevation loss after which a course would no longer be recognized for BQs, even if the distance was certified...

Oh, and the wheel is frequently checked throughout the course measurement process for accuracy (the standard method for calibrating a wheel is to wheel out 50m next to a metal 50m tape to confirm the accuracy and tune the wheel if necessary, the metal tape is used, since cloth tapes are prone to stretch).

I see what you are getting at, but all three of the Ironmans I've done were multi-loop with a random 180 degree u-turn somewhere on the course, that spot could very easily be moved in or out to get the distance to an exact certified 26.2. I've never understood how courses that include a random u-turn in the middle of nowhere (on the bike or run - looking at you IMTX bike course) can't get their distances correct.

How are you sure their distances are not correct? Measuring with a calibrated wheel is far more accurate than GPS, so just because your GPS is off a bit from the advertised distance doesn't mean that it isn't accurate. GPS sampling rate affects this especially in sections that are not straight each sample it takes are joined by a straight line (the trade off for high sampling rate is battery life...), depending on frequency these samples are taken, and whether they are around corners, or on straightaways, that introduces errors in the routing and measurement of the path traveled.

Generally when I'm racing, if the distance on my GPS is within about 3% of the advertised distance, I assume that the distance was in fact accurate, it's when it goes well beyond that point that I then question the course accuracy.

Bq standard should ban those races, or require times from those races to be 10min faster.

So are you guys saying that as long as the marathon course is a certified distance, Boston will accept the time from it? That's a shame and a bit of respect being lost for the process if there isn't an "standard" elevation profile allowance in the qualifying process. IE- allow any downhill race as long as it's certified?

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Brooks Doughtie, M.S.
Exercise Physiology
-USAT Level II

Have you done a downhill Marathon? I just raced Reval Big Cottonwood and it was hell on earth. "1" athlete in the M40-44 qualified for Boston out of 77 finishers. I ran 10+ minutes faster at Boston in 2018.

You look at the number of qualifiers from Berlin 2018?

yeah I think Boston relies on USATF certification in the US (other governing bodies in other regions/countries).

My immediate thought was that since USATF notes whether marathons are 'record eligible' that could be an easy way to knock out those downhill marathons... of course the issue is that Boston itself is NOT record eligible.

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808 > NYC > PDX > YVR
2024 Races: Taupo

USATF just certifies distance. I AAF dictates if it is Olympic qualifying or WR eligible. Iaaf does not allow more than 1m drop per 1km