The calculated distance (air line) between Yŏnmu and Songgangdong is approximately 26 miles respectively 42 kilometers.
By car or train, the actual journey to Songgangdong is certainly longer, as only the direct route (as the crow flies) between Yŏnmu and Songgangdong has been calculated here.
Air line (approximately)
42 kilometers
23 nautical miles