How Do You Measure Snow Fall?

Erie International Airport reported 2' of snow. I measured 23" but that was this afternoon after it had settled. We usually get more out here away from the lake. From what I can figure over the last 48 hours we have had almost 3' come down. I know there is a scientific formula for measuring it, but I did not take the time to do so other than use my tape measure. The snow that fell last night was huge and fluffy and the snow yesterday morning was wet and heavy.