The calculated distance (air line) between Seongnam-si and Chinch'ŏn is approximately 44 miles respectively 70 kilometers.
By car or train, the actual journey to Chinch'ŏn is certainly longer, as only the direct route (as the crow flies) between Seongnam-si and Chinch'ŏn has been calculated here.
Air line (approximately)
70 kilometers
38 nautical miles