The calculated distance (air line) between Hyesan and Sŭngjibaegam is approximately 34 miles respectively 55 kilometers.
By car or train, the actual journey to Sŭngjibaegam is certainly longer, as only the direct route (as the crow flies) between Hyesan and Sŭngjibaegam has been calculated here.
Air line (approximately)
55 kilometers
30 nautical miles