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Measurement of a track marathon

M mikesandfordMember
Yesterday, I had to measure an uncertified 400m track for a track marathon. As others have frequently found the track owner, Harrow School, did not have any documentation certifying the track length. The grounds manager apparently has a CD file with measurements from when the track marking company laid out the lines back around 2004, which he is going to send to me, but in the mean time we taped the track.

It is a beautiful 8 lane track and appears in the UK track directory here. The track has a raised kerb on the inside of lane 1. We were able to run the tape against it and tension it properly with a sping scale.

I took two measurements of one lap, yielding, after correction for temperature and the running line, 399.966m and 399.968m. So the average was 3.3 cm less than 400m. The UKA/IAAF standard for a certified track is a length between 400m and 400.04m so my result is a little short of what the track should be if properly laid out. However steel taping is not as accurate as a surveyor's total station instrument placed on the centre points of the semicircles and used to measure the radius of each he semicircle along 14 directions. The IAAF measurement report form shows what has to be done.

Here is an extract from my measurement report showing the data and some pictures of the track. Two of the tape lengths showed rather a large variation of 1cm, but overall the agreement was good. I had to decide on what to use as a short course prevention factor. I chose 0.03% on the following basis:
  • The class II tapes which I used are specified to have markings accurate to 0.02%
  • I had to add a bit more to accommodate errors in temperature correction, tensioning and tape positioning and reading so I added 0.01% for that (i.e. 4 cm in 400m)


The result was that I certified the marathon to be 105 plus 1/2 laps plus 11.15 metres.

As an alternative method I did try with my laser rangefinder to measure the width between the straights but the wind was blowing and the plumb bob could not be reliably placed accurately over the kerb edge. I would not have been able to attempt to measure the maximum length between the apexes of the semi-circles, since the long jump pit cover was in the way (see photo in the report) and the groundsman was unwilling to have it moved. I would have liked to have tried with the laser the method described in another thread on this forum but that will have to wait until I have a means of protecting the plumb bob from the wind.
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M mikesandfordMember
Duane,
Thanks for emphasising the correction for the distance of the running line from kerb which needed adding.

My kerb measurement was 398.082 m and I added 2 x pi x 0.3 m = 1.885 m which gave my result of 399.967 m.

One thing I want to correct in my account above: I said long jump pit cover, I meant high jump landing area cover. The metal cover was about 4 foot high completely blocking the line of sight between the apexes of the two semi-circular bends.
M mikesandfordMember
quote:
SCCF

Not sure what this means if it is not a typo for Short Course Prevention Factor.

I made up my own SCPF for this taping. I thought the normal bike SCPF of 0.1% was too high.

I argued that class II tapes have an marking accuracy of 0.02%.

I then added 0.01% for our taping accuracy (to cover temperature and tension inaccuracies as well as accuracy of placing the tape against the marks). 0.01% is 5 mm in every 50 m tape length which I think is an adequate allowance.

So the total SCPF which I applied was 0.03%.

What do people think about the appropriateness of that amount?
pastmemberpastmemberMember
SCPF. Sorry for my error.

Your logic and your methodology seems unassailable to me, Mike. I am just trying to learn what the historical IAAF criteria are for his kind of measurement. I can guess that your .03 should be adequate for a track, where the vagaries of the precise running route can be expected to be less an issue than on roads. Is this your rationale?
M mikesandfordMember
OK.

The running route is very clearly defined in this case by the kerb. The rule for road running ( and incidentally for track races) is measure 30cm from the inside kerb on bends. There is no vagary in following the running route here that needs to be covered at all by the SCPF, because I measured exactly on the kerb and then calculated the addition for the running line positioned 30cm out from the kerb.

Of course the running line should be similarly clearly defined for a road race by the boundaries of the available road. However, may be the measurer does not ride his bike exactly along the Shortest Possible Route along the road so that would one extra thing that has to be covered by the larger SCPF 0.1% which we use for bike measured courses.

I have not seen any criteria from the IAAF for measuring a marathon on a track. The IAAF document I referenced requires a surveyor to make measurements with a total station to show the the running line of lane 1 lies between 400 metres and 400.04 metres - a total range of only 4 cm. To get this accuracy of survey IAAF requires you to use an expensive total station set up at the centres of the semi-circles and check the radius at 14 points along each semicircle. Many tracks have not done this and so dont have IAAF certification. My measurement goal here was just to get the marathon the right distance, i.e. at least 42195m. not to certify the track properly for track races.

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