The calculated distance (air line) between Ansan-si and Gyeongsan-si is approximately 148 miles respectively 239 kilometers.
By car or train, the actual journey to Gyeongsan-si is certainly longer, as only the direct route (as the crow flies) between Ansan-si and Gyeongsan-si has been calculated here.
Air line (approximately)
239 kilometers
129 nautical miles