The calculated distance (air line) between Iwŏn-ŭp and Songjianghe is approximately 142 miles respectively 229 kilometers.
By car or train, the actual journey to Songjianghe is certainly longer, as only the direct route (as the crow flies) between Iwŏn-ŭp and Songjianghe has been calculated here.
Air line (approximately)
229 kilometers
124 nautical miles