The calculated distance (air line) between Namyangju and Yangp'yŏng is approximately 18 miles respectively 29 kilometers.
By car or train, the actual journey to Yangp'yŏng is certainly longer, as only the direct route (as the crow flies) between Namyangju and Yangp'yŏng has been calculated here.
Air line (approximately)
29 kilometers
16 nautical miles