The calculated distance (air line) between Sinmak and Sangsŏng-ni is approximately 63 miles respectively 101 kilometers.
By car or train, the actual journey to Sangsŏng-ni is certainly longer, as only the direct route (as the crow flies) between Sinmak and Sangsŏng-ni has been calculated here.
Air line (approximately)
101 kilometers
55 nautical miles