It's supposed to be warm here, this week, but we still have ice covering my calibration course. May get out to measure next weekend, though.
I think the soft surface had a definite impact on the length, but would doubt that half a mile of soft course would yield a course 180 meters long. That's about 22% (of the soft-surface destance). On a half-mile course, I would expect a 'soft-factor' variance of maybe 2%, at most. This is based on some rides I did where I had a concrete path, next to a cinder trail. Definite slippage on the cinders of about 1%. Add mud, and maybe 2%.
I think the biggest difference is due to the GPS.
If the majority of a course is on soft surface, I am leaning towards suggesting we calibrate on the soft surface. Do a hard-surface calibration, so we have a baseline, including just a 30-meter length, so wobble is factored-in. Then, do a one-tape-length strip on the soft surface, and compare the two. A longer calibration would be preferable, but may not be practical. Calculate the difference, and adjust accordingly.
While (as Jay said) records may not be set on these courses, it would still be a better product if we made the effort to make them the proper length, not just fall-back on "at least as long as the stated distance", and have a course such as this 1.7% long, instead of just .1%. (I subtracted the SCPF from 180m, since, in a perfect world, the course would be 10 meters long, anyway.)
Thoughts?