The calculated distance (air line) between Sŭngho 1-tong and Kosan is approximately 78 miles respectively 126 kilometers.
By car or train, the actual journey to Kosan is certainly longer, as only the direct route (as the crow flies) between Sŭngho 1-tong and Kosan has been calculated here.
Air line (approximately)
126 kilometers
68 nautical miles