Baseline (maritime law)

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The baseline is the basis for determining the sea zones named in the United Nations Convention on the Law of the Sea (UNCLOS) .



The seaward national territory of a coastal state belongs to the sea zones ; this is called the territorial sea . A maritime boundary is thus established by means of the baseline . Territorial sea of the State has full sovereignty ( sovereignty ).

Furthermore, with the help of the baseline, further sea zones defined in international maritime law, in which a state can exercise sovereign rights but which do not belong to the national territory, are delimited:

All parts of the sea lying inland from the baseline are referred to as inner waters . These belong to the national territory and are subject to the unrestricted sovereignty of the coastal state. In contrast to the territorial sea, there is no right of peaceful passage here .


Zones under the Law of the Sea according to the Convention on the Law of the Sea

The baseline is determined by the respective coastal state. The so-called normal baseline is the low-water line along the coast entered on the officially recognized large-scale sea ​​charts .

The baseline can be determined using the straight baseline method on coasts with deep indentations, bays, estuaries or with offshore island chains . Suitable points of the normal baseline are connected by straight lines, whereby the resulting baseline must not deviate significantly from the general course of the coast (Art. 7 UNCLOS). This scheme can, for. B. are used for bays and inlets with an opening to the open sea of ​​less than 24 nautical miles (Art. 10 para. 4 UNCLOS) or for river mouths (Art. 9 UNCLOS). Similarly, the straight baseline method can be used when offshore islands form a “parallel coast”, hence a lateral sea that is not connected to the open sea at a width of more than 12 nautical miles . The use of the straight baseline method creates internal waters (see above).

In the case of archipelagos, the archipelago waters can be included in the baselines, for which separate rules apply.

The baselines or the boundaries derived from them must be entered in the state's nautical charts or given as a directory of geographical coordinates and published. A copy of the nautical chart or directory must be deposited with the Secretary General of the United Nations .


When establishing its maritime borders in the North and Baltic Seas, Germany made extensive use of the straight baseline method. The coordinates of the baselines and the seaward boundaries of the territorial sea are published in the maritime boundary maps No. 2920 (North Sea) and 2921 (Baltic Sea) of the BSH . This determination method using geographical coordinates ensures that changes in the determination of the low water reference - e.g. B. changing the chart zero to Lowest Astronomical Tide (LAT) - have no effect on the boundary.


See also