The calculated distance (air line) between Kangdong-ŭp and Hŭngnam is approximately 95 miles respectively 153 kilometers.
By car or train, the actual journey to Hŭngnam is certainly longer, as only the direct route (as the crow flies) between Kangdong-ŭp and Hŭngnam has been calculated here.
Air line (approximately)
153 kilometers
83 nautical miles