Trackball motion tracking

[lemiant]

Hi everyone,

I have been thinking for a while about a good way to track robot motion in all directions, I have considered mice, but apparently lazer ones are illegal, and optical ones unreliable. So I've moved on to something more like a trackball, it could be mounted between the front wheels and lightly pressed against the ground using some kind of elastic force. What are your thoughts? Also does anyone know of a trackball-esque device that could handle speeds up to 16 fps? After a couple of hours of looking, the best I could find was 30in per second, which is nothing to an FRC robot.