Baseline (sea)

This article is about the nautical concept of baselines. For other uses, see Baseline (disambiguation).

A baseline, as defined by the United Nations Convention on the Law of the Sea, is the line along the coast from which the outer limits of a state's territorial sea and certain other maritime zones of jurisdiction are measured, such as a state's exclusive economic zone.^[1]

Maritime Zones under International Law

Measurement of baseline

Chilean Baseline, an example of straight baseline use

The following methods are used to measure a baseline under the Law of the Sea Convention. In all cases, the baseline is drawn according to the state's own charts.^[1]

Normal baseline

In most cases, the baseline follows the low-water line of the coastal state. There are a variety of special rules and exceptions for a range of geological features, including bays, ports, rocks, artificial structures and reefs.^[2][1]

Straight baselines

The UN Convention allows for straight baselines to be drawn where deeply indented coastline and fringes of islands are closely connected to the coastline. Straight baselines must be drawn between the features and the coastline, in the general direction of the coast, and cannot be drawn across low-tide elevations. The Convention also prohibits straight baselines that would cut off another state's access to territorial sea or Exclusive Economic Zone. Since their introduction, countries including Canada and China have used straight baselines to extend their maritime borders.^[1]

See also

• Territorial waters
• Exclusive economic zone
• Continental shelf
• International waters
• United Nations Convention on the Law of the Sea