How Nike+SportWatch GPS calibrates its foot sensor automatically using GPS

The Nike+SportWatch has no manual calibration of the foot sensor as the Nike+Sportsband does. As I surmised in my first review here is how they do it.

From official response by  Nike on Nike Forums

"Thanks for asking about the calibration and how it works.

You're correct in noting that there isn't any manual calibration, as there is with other devices, where you actually tell your device, "I