Ok, so I'm using an arduino with an led matrix and a homemade pressure sensor to figure out the height of a vertical jump and then display the info back. First I get the amount of time between when the person left the board and when they land back on it. I then divide the time in half and use the equation: Yf = 1/2 * g * t^2 substituting g for 386.088 inches per second^2 giving Yf = 193.044 * t^2 My problem now comes in here. I'm doing this inside a room with an 8 foot ceiling for easy reference on how high I am jumping. I'm 6' 1" so when I jump so that my head just barely touches the ceiling my vertical is roughly 23". The arduino, though, is reading a little over 16". My first thought was that the pressure pad was staying down for some time after I jumped, but I recorded a jump and it's working right starting the time right when I leave the pad. In fact I even used the time I got from comparing when I left the ground on the jump and when I landed in the video and got .58 seconds. Using the equations before that gives a little over 16 inches max height (like what the arduino measured). So, does anyone have any idea what's going on here?