- Hydrographic Service
- Geodesy and Tides
The United Nations Convention on the Law of the Sea (UNCLOS) 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 support role for the convention. The outer limit of a claim usually is a line at a constant distance from the baseline, expressed in nautical miles (M). One nautical mile corresponds to 1852 metre.
The support role is described in publication S51 of the International Hydrographic Organisation (IHO). 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). All laws and treaties mentioned on this web site are available at the legal database of the Netherlands government.
The Dutch baseline is a combination of normal baselines and straight baselines. Straight baselines are established by law. They close estuaries, 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. Depths are published on nautical charts with repsect to a chart datum (reference level), currently often the Lowest Astronomical Tides (LAT). Large-scale charts are charts that are covering a small area, and therefore have a relatively small reduction in size. Both the paper charts and the electronic charts (ENC) are official. For the Dutch normal baselines, paper charts are used at a scale larger than 1:150,000, and ENCs in the Usage Bands "Approach" and "Harbour".
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). The equidistance line is the line that connects all points at an equal distance from the baselines of both the nations.
News on maritime boundaries is available via the International Boundary Research Unit (IBRU) of the University of Durham. International treaties and national maritime claims are listed on the Maritime Space website of the Division of Ocean Affairs and the Law Of the Sea (DOALOS) of the UN.