Baseline (sea)

A baseline, as defined by the United Nations Convention on the Law of the Sea, is the line along the coast from which the seaward limits of a state's territorial sea and certain other maritime zones of jurisdiction are measured, such as a state's exclusive economic zone. Normally, a sea baseline follows the low-water line of a coastal state. When the coast is deeply indented, has fringing islands or is highly unstable, "straight" baselines may be used.
Measurement of baseline.
The following methods are used to measure a baseline under United Nations Convention on the Law of the Sea 1982.
Normal baseline.
Except where otherwise provided in this Convention, the normal baseline for measuring the breadth of the territorial sea is the low-water line along the coast as marked on large-scale charts officially recognized by the coastal State.
Reefs.
In the case of islands situated on atolls or of islands having fringing reefs, the baseline for measuring the breadth of the territorial sea is the seaward low-water line of the reef, as shown by the appropriate symbol on charts officially recognized by the coastal State.