The calculated distance (air line) between Donghae City and Hongch’ŏn is approximately 68 miles respectively 109 kilometers.
By car or train, the actual journey to Hongch’ŏn is certainly longer, as only the direct route (as the crow flies) between Donghae City and Hongch’ŏn has been calculated here.
Air line (approximately)
109 kilometers
59 nautical miles