some resorts have guys with radar guns in slow skiing zones, so if u want u could like blow by him on one run, then on the next run stop and ask him how fast u were going
hit a jump, if you case it, your not going fast enough and need to go faster. if you over shoot, your going to fast or popping to hard, slow down and pop softer.
count the number of people you pass and divide it by the sum of the run length and snow friction. then subtract the mph of wind. after that get blazed and watch fantasia and forget that you even care, because you shouldnt.
You can buy hotwheels radar guns at like zellers or toys r us for about 30-40$ and they are actually pretty accurate. I know someone who uses 1 for longboarding