The Chinese Late Ming Dynasty Courier Route System application calculates the total distance between postal stations, the number of postal stations visited, and the number of counties (circa 1911) that were crossed. You can select postal stations from the pull-down menu or pick them by clicking on the map. Click the gear icon to calculate a new route and the trash icon to clear an existing route. More data info at: https://worldmap.harvard.edu/maps/china-history/Kkj