Something I’ve known for years is that *somewhere* along the route, nearly 3/4 of a mile disappears. It doesn’t matter what cycle computer or what GPS I’m using by the time I hit the mile markers near the end of my ride I’m always off by that much.
I leave mile marker 14.69 and the following mile markers hit at (as expected) 1 mile intervals give or take a few hundred feet.
But when I hit mile marker 25 (ostensibly a little over 10 miles into the ride) I find that my various measuring instruments universally agree that I’m really only a bit over 9 1/2 miles along.
The other day I finally decided to take note of where and by how much the variance occurs. My new cycle computer combines both GPS info with the usual magnetic wheel speed sensor and is about as accurate as anything that is going down the trail.
As I mentioned, it’s not unusual for most mile markers to be off by a couple hundredths of a mile either way and it pretty much averages out.
However between mile markers 21 and 22 I have measured the distance to be about .82 miles, between mile markers 22 and 23 the distance is .76 miles, and between mile markers 23 and 24 the distance is about .7 miles.
Altogether these represent about .74 missing miles.
Not a big deal in the scheme of things.
But if you’re timing your performance against these mile markers, this could explain those spectacular rides / runs between mile markers 21 and 24…