The calculated distance (air line) between Changyŏn and Pyŏksŏng-ŭp is approximately 29 miles respectively 46 kilometers.
By car or train, the actual journey to Pyŏksŏng-ŭp is certainly longer, as only the direct route (as the crow flies) between Changyŏn and Pyŏksŏng-ŭp has been calculated here.
Air line (approximately)
46 kilometers
25 nautical miles