The calculated distance (air line) between Goyang-si and Gyeongsan-si is approximately 165 miles respectively 265 kilometers.
By car or train, the actual journey to Gyeongsan-si is certainly longer, as only the direct route (as the crow flies) between Goyang-si and Gyeongsan-si has been calculated here.
Air line (approximately)
265 kilometers
143 nautical miles