The calculated distance (air line) between Cheonan and Yangp'yŏng is approximately 51 miles respectively 82 kilometers.
By car or train, the actual journey to Yangp'yŏng is certainly longer, as only the direct route (as the crow flies) between Cheonan and Yangp'yŏng has been calculated here.
Air line (approximately)
82 kilometers
44 nautical miles