The calculated distance (air line) between Sŭngho 1-tong and Wŏnsan is approximately 79 miles respectively 128 kilometers.
By car or train, the actual journey to Wŏnsan is certainly longer, as only the direct route (as the crow flies) between Sŭngho 1-tong and Wŏnsan has been calculated here.
Air line (approximately)
128 kilometers
69 nautical miles