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