The calculated distance (air line) between Wŏnsan and Sangsŏng-ni is approximately 30 miles respectively 48 kilometers.
By car or train, the actual journey to Sangsŏng-ni is certainly longer, as only the direct route (as the crow flies) between Wŏnsan and Sangsŏng-ni has been calculated here.
Air line (approximately)
48 kilometers
26 nautical miles