Exact Marathon Distance?

42.155

42.195

doug225550 wrote:

42.195

doug is correct!!!

it is exactly 26 miles.

grun wrote:

doug225550 wrote:

42.195

doug is correct!!!

Although there will be an additional 0.1% short course prevention factor.

I could be wrong, cuz I have only been running a couple months, but the guy I run with says there is no official distance and that most are about 26 1/4 miles, but that they can be from about 22 miles to about 27 miles.

26 miles is 1,647,360 inches. Plus 385 yards which is 13,860 inches. Total: 1,661,220 inches in a marathon. There are 39.37 inches in a meter. Therefore dividing the two yields 42,195.072 meters in a marathon.

>> 26 miles is 1,647,360 inches. Plus 385 yards which is 13,860 inches. Total: 1,661,220 inches in a marathon. There are 39.37 inches in a meter. Therefore dividing the two yields 42,195.072 meters in a marathon. <<

Almost correct there is 39.3700787402 inches in 1 meter

This would give 42194.988 meters in a marathon.

Even that 39.3700787402 is not EXACT. The last 2 has been rounded up. One inch equals EXACTLY .0254 of a meter, so proclaimed by the scientific poo-bahs. The 39.37etc etc # is the reciprocal of .0254. What this means is that previously-mentioned 42,194,988 meters is the EXACT answer as it is the product of .0254 times the exact inches of 1,661,220.

As to the exact reciprocal of .0254, I hand calculated out to:

39.37007874015748031, then I got tired of waiting for the inevitable repeating number group that is always there when you divide one rational # by another rational #. For example, 1 divided by 7 is .142857 142857 142857....., with those 6 #'s then repeating as a group forever.

Now THAT was pretty boring A know !

Most large marathons due to human error are between 24 and 28 miles. After 30 years of the current roadracing era, race directors have been unable to make their races any more precise than this.

mr obvious, that just can't be so unless the race planners are absolute idiots... you are talking over 15 % variability here ! Even using a car odometer will get you inside of 3 %, and a well calibrated bicycle odometer will be inside of 1 %. And I believe all big marathons can/should be USATF-certified, and surely thir requirements must be quite stringent.

The "marathon" distance is 26 miles 385 yards. The IAAF/Aims recognizes the distance as 42.195 kilometers.

The previous posting is correct- the only exact conversion is using 2.54cm = 1 inch exactly.

All certified courses are measured with a short course prvention factor of .1%= 42.195m for a marathon (10 meters for a 10k).

Course measuring methods and standards have been universally applied and accepted since the early 80's. All good measurers will come up with a independent measurment of within 10 meters of each other over the marathon distance. This would results in a measurement of anywhere from 10m+/- the 42.195km (+42 meters short course prevention factor). It is a very unusual situtation for any major marathon not to be at this distance. The family of international measurers take great pride in their ability to produce accurate courses.

Regards,

David Katz

IAAF Technical Committee

IAAF "A" Measurer

Measurer since 1976

Thgank you David, that is good information from a highly credible source.

26.21875 miles.

I would love to hear some about how you actually go about this type of measurement, David. I can't imagine the attention to detail that it would take to provide that level of accuracy over 26 miles, on roads, usually with hills and several turns.

I'm not David but am an IAAF 'A' measurer so'll give a shot at a simplistic answer. In plain English:

First: a bike w/a Jones counter rides over a minimum 1000' calibration course.

Second: numbers from the cal ride are used to determine how many counts per mile, total distance, etc.

Third: after it's determined how many counts are needed per mile/km, add the .1% SCPF (short course prevention factor) to counts needed.

Third: ride the course following the SPR, shortest possible route (imagine a string laid out over the entire course, then pulled taut against curbs), stopping to mark miles/kms.

Fourth: ride course again, noting number of counts to each mile/km previously marked.

Fifth: ride over cal course again.

Sixth: if both rides don't agree w/in .08%, you gotta do it again.

Depends where the runner runs, lines, angles, aid stations etc but go with 42.195k

scotth wrote:

I'm not David but am an IAAF 'A' measurer so'll give a shot at a simplistic answer. In plain English:

First: a bike w/a Jones counter rides over a minimum 1000' calibration course.

Second: numbers from the cal ride are used to determine how many counts per mile, total distance, etc.

Third: after it's determined how many counts are needed per mile/km, add the .1% SCPF (short course prevention factor) to counts needed.

Third: ride the course following the SPR, shortest possible route (imagine a string laid out over the entire course, then pulled taut against curbs), stopping to mark miles/kms.

Fourth: ride course again, noting number of counts to each mile/km previously marked.

Fifth: ride over cal course again.

Sixth: if both rides don't agree w/in .08%, you gotta do it again.

I am not "A" certified but I have been through the measurement process a number of times, including the multiple version recounted well (especially for the "short version", since there is more detail). It was my understanding that around curves, the course was marked 1 meter out from the curve. In track races, the lane lines are measured 8 inches out from the marked lane line except for the inside lane, which has a curb and is marked 12 inches in. It seems realistic, given the track measurement that the 1 meter rule is still in effect, but I do not know this to be the case for sure.

Also, while the marathon distance was "officially" set at 26 miles 385 yards (26.21875) I am pretty sure that the official distance is now 42.195 km (not that it makes a difference given the documentation of the minimal difference).

As for the original post and the statements about not having a standard distance, that was only the case very early on although early courses were usually about 25 miles long. At the London Olympics (1924?), the course was set out and then the decision was made to allow the start (I think, it might have been the finish) to be viewed by the Royal children at the Palace, the race was made 26 miles 385 yards. It has stuck to this distance generally since.

As for those course measurements, they did get better and better in the 1980s. One interesting story is that they realized that the measurement for the NY City Marathon followed Blue line on the path but that this was not the shortest distance. As a result, Alberto Salazar lost his official (point-to-point) marathon mark, although the error was pretty modest (~40 meters?). Of course, I also remember Salazar cutting those corners (in his close race with the Mexican runner, name?).

Some of this is from memory and it fades a little when you have 55 years of stuff in there.

David Katz wrote:

All certified courses are measured with a short course prvention factor of .1%= 42.195m for a marathon (10 meters for a 10k).

David-

Reading that this 42.195m "short course prevention factor" is built into the measurement process made me wonder:

When the mile markers are measured/placed, where does that 42.195m get distributed? Is it equally distributed throughout the 26.2M/42.195K, or is it tacked on at the end?

Because otherwise, if the course is exactly accurately measured, and each mile is accurately placed, the distance after the 26 mile mark would be 42.195m long. That might not seem like a big deal, but if you were trying for a certain time (2:22, 2:20, 3:00, whatever), you'd be dealing with an extra 42.195m at the end of the race, which could certainly mean the difference between dipping under your personal barrier of choice. In this example of the perfectly measured course through 26M, if one was running along at 2:22 marathon pace, there would be an extra 8+ seconds to make up over the last portion of the course.

I know - not a big deal, but I'm just curious.

BDG