I will supply the minimum information necessary, and include as much obfuscation as possible.
A couple weeks ago I measured a course with a new measurer to teach him the tricks of the trade. Early in the morning I gathered up my materials, hung my bike up on the rack on the back of my vehicle, and drove 80 miles to a location near his home. I met up with him there, and we measured out a 315-meter calibration course at that location. Just as we were finishing it started to rain, so we went back to our separate cars where we waited it out. About 20 minutes later the rain stopped so we got out and did our pre-cal rides. Then we gathered up our stuff, hung our bikes on our racks, and each drove the 40 miles back towards my house where the race course was located.
At the race course location we found the desired start/finish, and then rode from there together to measure the 5k course. The course had a turn-around that we would be adjusting, so we stopped at the google-earth-determined point, spun our bikes around, and continued with the measurement until we got back to the start/finish. The course ended up being a few meters long, so we drove back to the turn-around and mile marks to adjust with our bikes. After we were all done we put our bikes back on our racks, and he drove back to the original cal course to do his post cal, while I drove 40 miles home to do my post-cal on my home cal course.
After I finished my post cal I pulled out my laptop in order to enter all my data into a spreadsheet, and that's when I noticed something strange. As I was entering my data I noticed that my pre-cal started with 262000 and ended with 280747, with the rides averaging out to about 3750. The starting count of my course measurement was 222000 and it finished at 281660. The start count of my post-cal was 264000 and the finish was 279557, with an average of about 3560.
I stared at these numbers for a long time trying to figure out how they were possible. I tried all kinds of combinations of how I might have transposed digits when I wrote the starting counts down for one, or all, of the measurements, so that the start counts of the second and third measurements were not smaller than the finish counts of the previous measurements. I couldn't come up with anything. And then suddenly it hit me, and all was right again in my measuring world.
What had happened with my numbers? If you know the answer, don't post it here. Write it on the underside of the frame of a Faraday Porteur electric assist bicycle with 8-speed internal hub shift, Gates belt drive, and steam-bent bamboo fenders, and send it to 323 Griggs Street, Rochester(our fair city), MI.
Seriously, if you do know the answer please don't post it here. Let others puzzle over it for a while like I did. Email me or private message me with the answer, and then after a couple days I'll post the answer here. You can post questions or requests for clarifications here though. Or maybe the answer is obvious to everyone. It wasn't for me.