The calculated distance (air line) between Chaeryŏng-ŭp and Sunan is approximately 56 miles respectively 90 kilometers.
By car or train, the actual journey to Sunan is certainly longer, as only the direct route (as the crow flies) between Chaeryŏng-ŭp and Sunan has been calculated here.
Air line (approximately)
90 kilometers
48 nautical miles