The calculated distance (air line) between Kyŏngsŏng and Sŭngjibaegam is approximately 48 miles respectively 77 kilometers.
By car or train, the actual journey to Sŭngjibaegam is certainly longer, as only the direct route (as the crow flies) between Kyŏngsŏng and Sŭngjibaegam has been calculated here.
Air line (approximately)
77 kilometers
42 nautical miles