Paul,
Accuracy is 'relative'. For HF, 'close' is 'good enough'
when
measuring the length of your antenna elements, since any formula
derived length is only a 'ball park' figure to start with. For
VHF/UHF element lengths that 'ball park' figure has to be
measured
more carefully, but it's still just a 'ball park' length. To
fine
tune an antenna's length requires 'checking'n'chopping' till you
get it exactly where you want it. Horse shoes and handgrenades
ain't the only things where 'close' counts...
'Doc