Re: It isn't that
Question for Charles Manning
My wife and her running colleagues are always complaining that their GPS watches (different brands) invariably under record the distance run in a measured event. Typically a 10km run would be shown as 9.9km or thereabouts. They get particularly annoyed when a Marathon (42.195km) is 'short', as many of statistics tracking sites they use won't recognise it as a Marathon.
I assumed this was because the sampling points were straightening out curves but you seem to say this may not be the case.
So what would cause the short recording of their runs?