The calculated distance (air line) between Sangsŏng-ni and Sinŭiju is approximately 147 miles respectively 237 kilometers.
By car or train, the actual journey to Sinŭiju is certainly longer, as only the direct route (as the crow flies) between Sangsŏng-ni and Sinŭiju has been calculated here.
Air line (approximately)
237 kilometers
128 nautical miles