The calculated distance (air line) between Changyŏn and Ganghwa-gun is approximately 83 miles respectively 134 kilometers.
By car or train, the actual journey to Ganghwa-gun is certainly longer, as only the direct route (as the crow flies) between Changyŏn and Ganghwa-gun has been calculated here.
Air line (approximately)
134 kilometers
72 nautical miles