The calculated distance (air line) between Sŭngjibaegam and Wŏnsan is approximately 161 miles respectively 259 kilometers.
By car or train, the actual journey to Wŏnsan is certainly longer, as only the direct route (as the crow flies) between Sŭngjibaegam and Wŏnsan has been calculated here.
Air line (approximately)
259 kilometers
140 nautical miles