The calculated distance (air line) between Wŏnsan and P’yŏngsŏng is approximately 84 miles respectively 136 kilometers.
By car or train, the actual journey to P’yŏngsŏng is certainly longer, as only the direct route (as the crow flies) between Wŏnsan and P’yŏngsŏng has been calculated here.
Air line (approximately)
136 kilometers
73 nautical miles