The calculated distance (air line) between Hŭngnam and Hyesan-dong is approximately 111 miles respectively 179 kilometers.
By car or train, the actual journey to Hyesan-dong is certainly longer, as only the direct route (as the crow flies) between Hŭngnam and Hyesan-dong has been calculated here.
Air line (approximately)
179 kilometers
97 nautical miles