Complex sentence: According to resolution of 1816, nautical charts produced by "Søkortarkivet" are indefinite copyrighted by the Danish government (normal copyright in Denmark is 70 years).
Split into simpler sentences: According to resolution of 1816, nautical charts produced by "Søkortarkivet" has no copyright expiring. They are permanently copyright protected by the Danish government (normal copyright in Denmark is 70 years).