The calculated distance (air line) between Ongjin and Chaeryŏng-ŭp is approximately 35 miles respectively 56 kilometers.
By car or train, the actual journey to Chaeryŏng-ŭp is certainly longer, as only the direct route (as the crow flies) between Ongjin and Chaeryŏng-ŭp has been calculated here.
Air line (approximately)
56 kilometers
30 nautical miles