4. SHORT COURSE PREVENTION FACTOR

There is a complication in the way in which we calculate the calibration constant which changes the values we used on the previous page.

Suppose a world best time was run on the 10k course we have just measured. An IAAF measurer might be called on to remeasure the course to confirm your measurement was accurate. Now suppose that during your measurement there were some small, unavoidable measurement errors (I shall explain the reasons for such errors later in the full seminar). Let us suppose that as a result of these unavoidable errors that you laid out the course 4m less than 10 km. ie the course is actually 9,996m even though your readings indicate 10,000m. This amount of error could easily occur.

Now let us suppose that IAAF measurer also has some errors in his measurements but he measures less and obtains a distance 3m less than the true distance. The true distance is 9,996 m and under these assumptions his measurement gives a value of 9,993m. so he will report the course to be 7m short of the 10 km. The world best time will be disallowed because the IAAF's rule 240 requires the course to be NOT LESS than the official distance for the event.

To allow for the typical small measurement errors a SHORT COURSE PRVENTION FACTOR (SCPF) is built into the calibration constant when laying out a course. This is done by multiplying the calibration constant by 1.001

Going back to the calibration constants calculated on the previous page and redoing the calculation including the SCPF we get:

  1. Pre measurement calibration = 351.35/ 671.53 * 1.001 rev. counts per m = 0.52373
  2. Post measurement calibration = 351.10/ 671.53 * 1.001 rev.counts per m = 0.52336
  3. Select the largest calibration constant = 0.52373 rev. counts per m
  4. Course length = 5,226/0.52373 = 9978.4 m

To make the course exactly 10 km I need to add (10,000-9,978.4) = 21.6 m. So you see including the SCPF means we add 9.9m on to this 10k course. This makes sure that even if we have made small errors the course will not be shorter than 10,000m.

From now on you must always multiply every calibration constant by 1.001 in order to include the SCPF. Show it in your working, so anyone checking your work can easily see it has been included.

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