The IHO defines the southwestern limit of the North Sea as "a line joining the Walde Lighthouse (France, 1 ° 55'E) and Leathercoat Point (England, 51 ° 10'N) ''. The Walde Lighthouse is 6 km east of Calais (50 ° 59 ′ 06 '' N 1 ° 55 ′ 00 '' E ﻿ / ﻿ 50.98500 ° N 1.91667 ° E ﻿ / 50.98500; 1.91667), and Leathercoat Point is at the north end of St Margaret 's Bay, Kent (51 ° 10 ′ 00 '' N 1 ° 24 ′ 00 '' E ﻿ / ﻿ 51.16667 ° N 1.40000 ° E ﻿ / 51.16667; 1.40000).
where does the english channel end and the north sea begin
a line joining the Walde Lighthouse (France, 1 ° 55'E) and Leathercoat Point (England, 51 ° 10'N)