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