The calculated distance (air line) between Ungsang-nodongjagu and Onsŏng is approximately 48 miles respectively 77 kilometers.
By car or train, the actual journey to Onsŏng is certainly longer, as only the direct route (as the crow flies) between Ungsang-nodongjagu and Onsŏng has been calculated here.
Air line (approximately)
77 kilometers
41 nautical miles