The function Telemeter (Stormeter) is noted on the dial or bezel of the Swatch models “Take Some Minutes - YCS481” and “Rosso Furore - YCS494G” (from the professional dictionary of watch-making)
It is an instrument for measuring distances. In horology, it is a timer or chronograph with a graduated dial enabling distances to be read off on the basis of the speed of sound through the air at 0°C., viz.333 1/3 metres per second. The time that elapses between the flash of an explosion (firing of a gun, lightning) and the hearing of the noise makes it possible to read off on the dial the distance between the observer and the position of the flash.Concretely, it means that when you see a flash (ex. thunder) and you count the time with your Chrono (ex. 6 seconds). On the dial it appears the distance of the flash: 2 Kilometres!