As an island continent, Australia has sovereign rights over a vast area of ocean, along with the fishery, mineral, and petroleum resources found in that area - resources worth billions of dollars each year.
The management and protection of the waters that yield these resources is, however, a complex task. Geoscience Australia has a major role in the delineation of Australia's maritime boundaries. The delineation of these boundaries has strategic, economic and environmental implications.
Delineating Australia's maritime boundaries
Geoscience Australia has developed, and currently maintains, an Australian Maritime Boundaries database. Australia's Maritime Boundaries (AMB) is now on-line via the Australian Marine Spatial Information System (AMSIS). This geographic information system includes the Territorial Sea Baseline (TSB) and the maritime zone limits derived from it. These data are used to assist Geoscience Australia provide advice to Government on the location of maritime boundaries and to facilitate the meeting of specific international obligations as set out in the United Nations Convention on the Law of the Sea (UNCLOS). Australia ratified the Convention on 5 October 1994 and became legally bound to its provisions when it entered into force on 16 November 1994.
The primary task for maritime boundary determination is the delineation of the baseline from which the outer limits of the various maritime zones are measured. This TSB consists of several components including normal baseline, straight baselines and bay and river closing lines.
Using digital mapping and charting data supplied by a number of Commonwealth and State government authorities, Geoscience Australia continues to validate the position of the TSB around the entire Australian coastline. This ensures that the TSB is consistent with the data supplied by those authorities and also with the requirements of UNCLOS.
The TSB is the 'marker' from which the outer limits of a number of maritime zones are computed. These include the 3 nautical mile limit of coastal waters, the 12 nautical mile limit of the territorial sea, the 24 nautical mile limit of the contiguous zone, the 200 nautical mile limit of the Australian Exclusive Economic Zone. As well, the outer limit of the extended continental shelf is sometimes based on a constraint line lying 350 nautical miles beyond the TSB.
The definition of the outer limit of the extended Continental Shelf is described in Article 76 of UNCLOS. Geoscience Australia's Law of the Sea and Maritime Boundaries Advice Project is responsible for the survey work, data processing and compilation, and interpretation and analysis to determine the necessary geological and geomorphological information to support the delineation of the outer limit of the extended continental shelf around Australia and its territories.
A cooperative project
The validation and upgrading of the TSB to its current high standard has been made possible with the cooperation and support of the Australian Hydrographic Office and all Australian State and the Northern Territory mapping agencies. This support includes provision of both hard copy maps and charts, digital mapping and chart data, aerial photography, other coastal data and advice. As well, many maps produced by the Royal Australian Survey Corps were used in the development of AMSIS.
The baseline and maritime boundaries produced by Geoscience Australia are developed in consultation with the Commonwealth Department of Foreign Affairs and Trade, and the Attorney-General's Department who also provide essential support and advice.
The legal framework
The UNCLOS establishes a comprehensive framework for the determination of the territorial sea baseline and the various maritime zone boundaries. The Convention entered into force on 16 November 1994, and embodies the notion that all problems of ocean space are closely interrelated and need to be addressed as a whole. Today, it is the globally recognised regime dealing with all matters relating to the law of the sea.
Domestically, the Seas and Submerged Lands Act 1973, declares Commonwealth sovereignty over the territorial sea and certain Commonwealth rights in respect of the contiguous zone, exclusive economic zone (EEZ) and continental shelf. In February 1983, a proclamation adopted the low-water datum known as Lowest Astronomical Tide (LAT) as the datum upon which the territorial sea baseline along the coast would be based. LAT is the low water datum used on Australian Hydrographic charts and is the lowest level that can be predicted under average meteorological conditions. The remainder of the territorial sea baseline consists of straight lines across river mouths, bays and areas of deeply indented coastline or where there are fringing islands along the coast. These lines are known as straight baselines and their terminal points were gazetted on 9 February 1983 in the Commonwealth of Australia Gazette No. S 29.
As well, the Offshore Constitutional Settlement (OCS) is an agreement between the Commonwealth and the States (concluded at the Premiers' Conference in 1979), which provides the basis for an agreed division of powers between the Commonwealth and the States in relation to coastal waters and in relation to certain other matters including the regulation of shipping and navigation, offshore petroleum exploration, crimes at sea, and fisheries. A range of legislation gives effect to the OCS at Commonwealth level.
What maritime boundaries data is available?
Australia's maritime boundaries are available as the Geographic Information System (GIS) data product known as Australian Maritime Boundaries (AMB) and can now be viewed on-line via AMSIS. Also available is a small scale map showing Australia's Maritime Zones.
The approximate location of the territorial sea straight baselines and outer limits of Australia's maritime zones, are also shown on miscellaneous chart Aus 65950 and Aus 65951, and on appropriate Australian navigational charts of 1:150 000 or smaller scale. The depiction of the outer limits of Australia's maritime zones on these charts is sourced from AMB or AMBIS 2001 Version 1.1 data. These charts are available from either the Australian Hydrographic Office or from an AHS product distributor.