I recently laid out my first calibration course. So far I have used it only to measure some of my training runs. I have some questions about the using my cal course for "real" measurements.
1. My calibration course is just over 300m (the minimum length). I could not fit a longer course in that location, and I picked the location because it is very concenient. Will having a minimal length calibration course cause me any grief?
2. The edge of the road is lined with a concrete gutter. I used the seams between the individual gutter pieces as my start/end points for the course. I am assuming this is ok?
3. Is there any reason to get the cal course certified now, or should I wait until I measure an actual race course?
1.-As far as the length is concerned there is really no problem with laying out a 300 meter course--it is reasonably accurate. I did ask Ted Corbitt about this when I met him and he said he really preferred to have one a half mile to mile of length. He just felt he was able to be more accurate that way.
2-As long as your marks are easily located again--not a problem at all. I am assuming that those seams are not approx. and are really exact. You want brutal accuracy here--those seams should be the exact spots you used your paint, nail and washer to reference.
3. Why not certify it? you can then just reference the course no. and include the course map for the cal when you measure the race course. Did you end up measuring the cal. course yourself or with another measurer? Did you do the paper work and notate the temp etc.? All of this info is fresh in your memory--I would submit it for certification. Besides--after you have applied for a cal course you just might get out there and do some preliminary rides for a race course and decide to certify a race course! In addition to race courses, I have measured some courses in my neighborhood for my own training and for practice too. Good luck and keep at it Rick.
I actually did record the temp and even filled out the cal course paperwork. I just have not submitted it.
I haven't seen anywhere a discussion of acceptable tolerances. For example, when my assistant and I measured the cal course, there was a 1 inch difference between the out and back measures. I thought that was pretty good (for a 300m course) but I have no data on the normal range of differences. So how good is 1 inch over 300m?
One inch in 1000 feet is pretty good agreement, about 1/10000. Two inches (1/5000) is about the edge of decent measurement with a tape.
As for the half mile calibration being more accurate than 300 m, that's true, but the difference is insignificant. If you had 10 people lay out a race course using a 300 m calibration course, and another 10 use a half-mile cal course, you would be hard pressed to find a difference between the two resulting courses. There would likely be more difference due to differing road surface roughness than length of the cal course.
The 300 m minimum length was brought in to encourage people to lay out calibration courses close to the race course. Too many people were driving 60 miles to a half mile cal course because it was too time-consuming to lay one out, even if you could find a straight half mile near the race course.
I have noticed that weather conditions affect the difference between the out and back calibration course measurements. When I and my two assistants measured a 500 meter calibration course in Detroit Lakes, MN last September, we had 500.000 meters each way. We measured back to the start mark within 2 mm. The temperature remained at 58 degrees F and it was cloudy. Whenever the temperature has changed during measurement, my out and back calibration course measurements have been different. I always have two people help me measure a calibration course.
I'm puzzled. If you measured back to the start within 2 mm, how could you have had 500.000 meters on each measurement? Wouldn't one of them have been 500.002 or 499.998?
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