Height Question

How do parks measure the height of roller coasters? Do they measure from the ground to the bottom of the track, to the train, or to the rails, or none of the above? Also what if the coaster is over water, do they measure from the bottom of the water or the top of the water?

from the point where the station is(not necessarily the actual station, but the level ground where the station is) to the heighest point of the track
-----------------
Up Your Nose With a Rubber Hose!

Parks can measure height any way they want.  I believe that Guiness measures from the highest point of the coaster to the ground underneath.  I'd be willing to bet that PKI didn't measure SOB from the station ground level since that is about 40 feet higher than the base of the lift hill.