Basic electrical touch surface

I am building a prototype vertical jump measuring device. Traditional vertical jump apparatuses measure how high the jumper reaches based on how many horizontal rods he was able to displace, as shown in my attachment. I am looking to develop a similar device, but replace the rod setup with a touch sensing surface. I only need the surface to be able to detect a hand's touch and measure how far the finger tip is from the edge of the surface. The surface size needs to be about 12 inches by 12 inches.