Access Digital Data	Creating and Updating Maritime Limits
Latest News	More About Maritime Limits and Boundaries

Access Digital Data

Latest News (top)

The Office of Coast Survey has completed a multi-year project to merge all of the regional maritime limits into a single seamless digital dataset. Because U.S. maritime limits change, based on accretion or erosion of the charted shoreline, Coast Survey, in conjunction with the U.S. Baseline Committee, continually maintains the dataset. When NOAA releases a new nautical chart the maritime limits and boundaries are updated as needed.
As of July 2012, the digital data and metadata are on version 3.1. New actions include:

• updated 12nm, 24nm, and EEZ limits in several regions of Alaska

Bookmark this site, as we will frequently update the dataset with new digital limits of the maritime zones. Official limits are superseded by the publication of a new chart edition.

Creating and Updating Maritime Limits: An Interagency Process (top)

The U.S. maritime limits are projected from a “normal baseline” derived from NOAA nautical charts. A “normal baseline” (as defined in the 1958 Geneva Convention on the Territorial Sea and the Contiguous Zone and Article 5 of the United Nations Convention on the Law of the Sea) is the low-water line along the coast as marked on officially recognized, large-scale charts. Since "low-water line" does not reference a specific tidal datum, the U.S. applies the term to reference the lowest charted datum, which is mean lower low water (MLLW).

The maritime limits are created using “envelope of arcs,” a method by which one would roll a virtual circle along the charted low water line and select salient points. These salient points are called contributing baseline points. Arcs generated from these baseline points are blended together to form a continuous limit line or envelope of arcs.

The U.S. Baseline Committee reviews and approves the limit of all maritime zones on NOAA charts. It gains interagency consensus on the proper location of the baseline, using the provisions of the 1958 Convention on the Territorial Sea and the Contiguous Zone, to ensure that the seaward extents of U.S. maritime zones do not exceed the breadth permitted by international law. Current members of the Committee include the Departments of State (Chair), Commerce (NOAA), Justice, Interior (BOEMRE), and Homeland Security (Coast Guard), among others.

 

More Information about U.S. Maritime Limits and Boundaries (top)

NOAA is responsible for depicting on its nautical charts the limits of the 12 nautical mile Territorial Sea, 24 nautical mile contiguous zone, and 200 nautical mile Exclusive Economic Zone (EEZ). These zones are highlighted in orange.

Territorial Sea
The territorial sea is a maritime zone over which the United States exercises sovereignty. Sovereignty extends to the airspace above and to the seabed below the territorial sea. The U.S. territorial sea extends 12 nautical miles from the baseline.

Contiguous Zone
The contiguous zone of the United States is a zone contiguous to the territorial sea. In this zone, the U.S. may exercise the control necessary to prevent and punish infringement of its customs, fiscal, immigration, cultural heritage, or sanitary laws and regulations within its territory or territorial sea. The U.S. contiguous zone is measured 24 nautical miles from the baseline. 

Exclusive Economic Zone (EEZ)
The exclusive economic zone (EEZ) of the U.S. extends 200 nautical miles from the territorial sea baseline and is adjacent to the 12 nm territorial sea of the U.S., overlapping the 12-24nm contiguous zone. Within the EEZ, the U.S. has:

• sovereign rights for the purpose of exploring, exploiting, conserving and managing natural resources, whether living and nonliving, of the seabed and subsoil and the superjacent waters and with regard to other activities for the economic exploitation and exploration of the zone, such as the production of energy from the water, currents and winds
• jurisdiction as provided for in international and domestic laws with regard to the establishment and use of artificial islands, installations, and structures, marine scientific research, and the protection and preservation of the marine environment
• other rights and duties provided for under international and domestic laws

(See Presidential Proclamation No. 5030, March 10, 1983.)
Certain U.S. fisheries laws use the term “exclusive economic zone” (“EEZ”). While its outer limit is the same as the EEZ on NOAA charts, the inner limit generally extends landward to the seaward boundary of the coastal states of the U.S. For the seaward limit of the states jurisdiction under the Submerged Lands Act, please see GIS Data / Shapefiles.

Maritime Boundaries
Maritime boundaries with adjacent and opposite countries are established through agreement and treaties with these neighboring nations. For more information about these treaties, visit the Department of State information page on maritime boundaries. 

Additional Information 
Download Maritime Limits White Paper
U.S. Maritime Zones Description in the Coast Pilot (pp. 32-34)
History of Maritime Zones under International Law
U.S. Maritime Boundary Treaties from Department of State

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