The calculated distance (air line) between Pukchil-lodongjagu and Hyesan is approximately 152 miles respectively 244 kilometers.
By car or train, the actual journey to Hyesan is certainly longer, as only the direct route (as the crow flies) between Pukchil-lodongjagu and Hyesan has been calculated here.
Air line (approximately)
244 kilometers
132 nautical miles