Derive position on paper using sound waves?

[deztox]

After watching the video below, I came up with the idea of using a piece of paper as a keyboard much like Mistry did for a mouse. I am only in high school, but I'm sure you can measure position via sine waves which relates to the sin trig function (the reason I posted here; if wrong thread, mods please relocate me) as I saw a mini-lecture about radar guns using Doppler/phase shift to calculate speed. My question is how do I do the calculations? Further (video) lecture material would be nice.

http://www.ted.com/talks/pranav_mistry_the_thrilling_potential_of_sixthsense_technology.html

 

[pat_connell]

Using a piece of paper as a keyboard is an interesting concept but it won't be easy to implement. You will need to use some type of sensor technology that can detect the position of your finger and map it to a key on the piece of paper. One way to go about this is to use capacitive sensing. Capacitive sensors work by detecting changes in electric field when an object is brought into contact with them. By placing these sensors on the paper, you can detect the position of the finger and map it to a key. Another option is to use a camera and some image recognition algorithms. This would involve placing a camera above the paper and tracking the position of the finger as it moves across the paper. This can then be used to detect the position of the finger and map it to a key on the paper. Unfortunately, calculating the position of the finger using sine waves is not a practical solution. It's possible to use Doppler and phase shift principles to measure speed, but it's not suitable for measuring position.