Another rip from the Edinburgh Hacklab archives (Definately go there if you get a chance!!!).
What do you do if you have a cheap Robot mechanism with all sorts of inaccuracy and slop but want
repeatable high levels of acuracy. Optical localisation is the answer work out where you are with a camera
on your hand ..simples
Tom et al did a good job of the article so I won't copy it all here ...take a look!