The calculated distance (air line) between Panghyŏn-dong and Hyesan is approximately 186 miles respectively 300 kilometers.
By car or train, the actual journey to Hyesan is certainly longer, as only the direct route (as the crow flies) between Panghyŏn-dong and Hyesan has been calculated here.
Air line (approximately)
300 kilometers
162 nautical miles