NJK, you could be right with your two comments. But thinking about it, at least my eventual outcome is some sort of consistency between my GPS using MMR and my BC, no???
You want to be consistent
and accurate (there's little point in being consistently inaccurate).
When you say “curvy path”, yes, I agree if there were lots of relatively “small” curves. But as I was measuring rides between 2km and 30+km with straights and curves, I would think that the impact of “curves” over those distances would be somewhat negligible when compared to the circumference of my tyre.
I think you are absolutely correct if I was riding “short” and “curvy” distances every time. But that is not the case.
I think I will start my third list next week and see what the outcome is. Maybe I could compare my third list measurements/distances with measurements on Google Maps or some other map to check if gentle* curves make any difference over “larger” distances.
* gentle road curves vs concentric or tight circles and curves.
Your bicycle is moving back-and-forth in places the GPS is (and you are) seeing as perfectly straight lines.