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Maritime Limits
The United Nations Convention on the Law of the Sea (UNCLOS) of 1982 establishes the rights that nations have at sea and the way in which neighbouring nations limit these rights. A central element in this convention is the baseline, which defines the location of the coast. This baseline is derived from nautical charts, which is the reason that hydrographic offices worldwide play an important role in the geographic work related to the convention. The hydrographic tasks are referred to as the technical aspects, as different from the legal aspects. The technical aspects are described in the fourth edition of publication S51 "A manual on technical aspects of the United Nations convention on the law of the sea" of the International Hydrographic Organisation (IHO). Appendix 2 contains Articles 1-123 and Annex II of UNCLOS. This publication is published by the Advisory Board on the Law of the Sea (ABLOS) of the IHO and the International Association of Geodesy (IAG). At the time of publication of the fourth edition, the International Oceanographic Committee (IOC) was also part of ABLOS. All mentioned IHO publications are available from the International Hydrographic Organization (IHO).
The outer limit of a claim is often a line at a constant distance from the baseline, expressed in Nautical Miles (M), a nautical mile being defined as 1852 metres. This definition is given in the fifth edition of publication S32 “Hydrographic Dictionary” available at www.iho.int, (see International Nautical Mile, index number 2516). The Hydrographic Service of the Royal Netherlands Navy is responsible for the technical aspects for the Kingdom of the Netherlands, comprising the Netherlands, Curaçao, Sint Maarten, and Aruba. Most of the laws and treaties mentioned here under are available in Dutch at www.wetten.overheid.nl.
The Dutch baseline is a combination of normal baselines and straight baselines. Unlike normal baselines, the straight baselines are not subject to change and are established by law. The straight baselines close estuaries and ports, thereby creating the boundary between the territorial sea and the internal waters.
The normal baselines are the zero metre depth contours, as shown on the most recent large-scale nautical charts. Large-scale charts are, according to the IHO, "charts that are covering a small area", and therefore have "a relatively small reduction in size"(S32, index number 4519). Both the paper charts and the electronic charts (ENC) are official and are used for the construction of the baseline. The Hydrographic Service publishes the new edition of paper charts and the corresponding ENC updates as closely in time as possible. This is done to prevent ambiguity. For the Dutch normal baselines, paper charts are used at a scale larger than 1:150,000, according to the third edition of IHO publication M4-B “Chart specifications of the IHO” (Article B-126). ENCs in the Usage Bands "Approach" and "Harbour" are also used.
Depths are published on charts with respect to a vertical reference level, or chart datum, which coincides with the lowest expected water level. Nautical charts of the North Sea are published with respect to the lowest astronomical tide (LAT). For more information see the LAT page at coordinate systems - vertical. As the Caribbean has a very limited tidal amplitude, the definition of chart datum is less critical for that region.
UNCLOS states that, in the absence of an established maritime boundary, a state is not entitled to a more distant claim than the equidistance line with another state (for the territorial sea (TS), Exclusive Economic Zone (EEZ) and Continental Shelf (CS), see Articles 15, 74 and 83, respectively). The equidistance line is the line that connects all points at an equal distance from the baselines of both the nations. For an overview of the lines and zones in the North Sea that have a relation with UNCLOS, see the web page maritime limits North Sea. For the lines and zones in the Caribbean that have a relation with UNCLOS, see the web page maritime limits Caribbean Sea. The lines and zones are available for downloading in several formats from the web page download maritime limits.
Relevant news and advice is available via the International Boundary Research Unit, University of Durham. International treaties and national maritime claims are listed on the Maritime Space website of the UN, at United Nations.
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