The calculated distance (air line) between Sangsŏng-ni and Changyŏn is approximately 115 miles respectively 186 kilometers.
By car or train, the actual journey to Changyŏn is certainly longer, as only the direct route (as the crow flies) between Sangsŏng-ni and Changyŏn has been calculated here.
Air line (approximately)
186 kilometers
100 nautical miles