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Question - How many counts is an acceptable number to be off in Counts per mile when using 2 different calibration courses? All rides were done in a span of 45 to 50 minutes.

1st Calibration course - 1000 feet

Start - 92658

1 - 96035 - 3377

2 - 99413 - 3378

3 - 102788 - 3375

4 - 106166 - 3378

Gives you an average of 3377 or 17848.39 counts per mile

2nd Calibration course - 1320 feet

Start - 14736

1 - 19196 - 4460

2 - 23656 - 4460

3 - 28116 - 4460

4 - 32578 - 4462

Gives you an average of 4460.5 or 17859.84 counts per mile.

Total difference between the 2 counts per mile is 11.45 counts. This seems a little high to me. I am wondering if anyone has used 2 different calibration courses and how much the 2 calibration courses were off?

So lets say I used Calibration course #1 to measure the 5k course. 17848.39*3.106856= 55452.38. I make sure the course is 55452.38 counts. Heading home my wife calls and says a big rain storm is at my calibration course so I get on the web site and find a calibration course close to were I am at and no rain so I do my 4 rides on calibration course number 2. Now I find out I am 10.51' short from what I measured and go back and correct the course.

Now lets say it is the other way around that i use calibration course 2 for the measurement  and use course 1 for the post calibration and now I would be 10.81' too long.

So is 11.45 counts per mile between the 2 rides too big of a difference or would that be an acceptable difference?

Thank you for any input on this and maybe I am looking at it all wrong.


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If the temperature hadn't changed I would suspect that one of the calibration courses is a bit off. Perhaps the temperature of the tape during measurement was not accurately accounted for or perhaps the tension on the tape during the measurement was too light or two heavy. 

I would go and remeasure both calibration courses. 

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