The calculated distance (air line) between Sŭngho 1-tong and Changyŏn is approximately 70 miles respectively 112 kilometers.
By car or train, the actual journey to Changyŏn is certainly longer, as only the direct route (as the crow flies) between Sŭngho 1-tong and Changyŏn has been calculated here.
Air line (approximately)
112 kilometers
61 nautical miles