The calculated distance (air line) between Yonggang-ŭp and Wŏnsan is approximately 110 miles respectively 178 kilometers.
By car or train, the actual journey to Wŏnsan is certainly longer, as only the direct route (as the crow flies) between Yonggang-ŭp and Wŏnsan has been calculated here.
Air line (approximately)
178 kilometers
96 nautical miles