HWD
Point taken, however the one I was making is that the Form 214 winds aloft data is usually so far out that any extra accuracy of the slide rule is wasted.
If you fly for 15 mins, that is 20-30 miles, and unless the area is peppered with clear and tall landmarks, if you are even slightly out you will probably not find the one you are looking for. If one is doing PPL-style visual nav, one needs to be monitoring progress more "as one goes along" than that.