The calculated distance (air line) between Yonggang-ŭp and Kanggye is approximately 158 miles respectively 255 kilometers.
By car or train, the actual journey to Kanggye is certainly longer, as only the direct route (as the crow flies) between Yonggang-ŭp and Kanggye has been calculated here.
Air line (approximately)
255 kilometers
138 nautical miles