A method of measuring dynamic air pressure on a ground surface beneath a negative air system which is comprised of a rotatable negative air pressure element with a deck unit having a top with side walls and an open bottom involves placing the system on an elevated horizontal platform
A method of measuring dynamic air pressure on a ground surface beneath a lawn mower system which is comprised of a rotatable horizontal blade with a deck unit having a closed top with side walls and an open bottom involves placing the mower on an elevated horizontal platform located in