The calculated distance (air line) between Hwangju-ŭp and Changyŏn is approximately 47 miles respectively 75 kilometers.
By car or train, the actual journey to Changyŏn is certainly longer, as only the direct route (as the crow flies) between Hwangju-ŭp and Changyŏn has been calculated here.
Air line (approximately)
75 kilometers
41 nautical miles