The calculated distance (air line) between Hamhŭng and Sangsŏng-ni is approximately 62 miles respectively 100 kilometers.
By car or train, the actual journey to Sangsŏng-ni is certainly longer, as only the direct route (as the crow flies) between Hamhŭng and Sangsŏng-ni has been calculated here.
Air line (approximately)
100 kilometers
54 nautical miles