My GPS is in statutory miles and the river floats are referred to in statutory miles. I think that the estimations on miles may have been made 50 years ago and they used a much more primitive means of calculation than our current GPS. Plus we never go in a staight line which would account for a lot of discrepancy. We are in the middle of the US so there are few opportunities to refer to things in other than statutory miles. I admit the Kilometer thing does make the distance sound cooler.