Resistive touch screen information

I’m interfacing this touch screen ( https://www.sparkfun.com/products/8977 ) with arduino uno. I used this tutorial to get things going http://kalshagar.wikispaces.com/Arduino+and+a+Nintendo+DS+touch+screen

All works fine, I can get readings of X and Y position. The problem is that I saw that X and Y position depend on how much pressure I put on the touch screen. So if I hold my finger on the touch screen I get a constant X and Y and when I keep my finger in the same place and just increase the pressure then X and Y coordinates seem to increase even if I don’t move my finger. Pressing harder looks like I’m moving the finger on the touch screen.
Is there a way to know the real coordinates even when the pressure changes ?

Thanks and a nice Christmas.

The fact is, that your finger doesn't touch the screen in an exact point, but on a small area. If you increase the pressure this Area increases due to the physiology of your fingers. but as a ressistive touchscreen can only read out one position, the reported position is not the actual position but some (random) position within this area. Which one depends on how the screen interprets multiple measurements. If your screen or value evaluation takes always the max measurement, your reported position will be X_reported = X_actual + r, while r is the radius of your the contact area. As the radius increases with pressure, the reported position increases, too.

Have you tried using something smaller than your finger and not so flexible as your finger as your input device (e.g. a pencil)? If yes is there the same behaviour?

What is the sampling frequency of your readings? Is the reported position constant or is there some noise, if you don't move your finger and don't change pressure?