I'm using Kinect to detect if my hand is going right, left, up or down to control the arrow keys on a keyboard. I use my hip joint (which remains static) as a reference. It is a bit hard to give a proper range to those movements since sometimes according to the coordinates the right-up position can be mistaken. The same for down-left. I thought of using Vector Mathematics to help with this problem but so far I haven't come up with any idea of how to implement 3D vector theory to help.
I mean: should I use the angle between two vectors to infer a particular position of my arm compared to my hip? Or a substraction? Any suggestions would come in handy!