Share 'LBL map for determining "n" values'

I am curious about the zone map developed by LBL that is used for calculating Building Tightness Limits (BTL)  The map is ubiquitous, but pretty crude.  It certainly doesn't correspond to avg wind speeds where I live.  Are there any other factors incorporated in that map?  Using the wrong zone can result in a 15-20% error in the BTL For reference, I'm attaching some maps from Montana Thanks, Jim