The calculated distance (air line) between Haeju and P’yŏngsŏng is approximately 84 miles respectively 135 kilometers.
By car or train, the actual journey to P’yŏngsŏng is certainly longer, as only the direct route (as the crow flies) between Haeju and P’yŏngsŏng has been calculated here.
Air line (approximately)
135 kilometers
73 nautical miles