> Fancier verniers instead have two tracks in parallel, with slightly different pitches. Checking the offset between the two patterns at the current location gi

> Fancier verniers instead have two tracks in parallel, with slightly different pitches. Checking the offset between the two patterns at the current location gives an absolute measurement. In your article you link to a patent on the cheaper T shaped coatings, do you also have a reference to a patent specifically using this system of parallel + different pitch tracks? Great write up by the way!