Worldwide at various scales

Sea level; Bathymetry and Elevation

Sea level recorders; single-beam echosounders

A series of approximately 3250 navigational charts covering the world. The series is maintained by Admiralty Notices to Mariners issued every week. New editions or new charts are published as required. Two thirds of the series are now available in metric units. In areas where the United Kingdom is, or until recently has been, the responsible hydrographic authority - i.e. Home Waters, some Commonwealth countries, British colonies, and certain areas like the Gulf, Red Sea and parts of the eastern Mediterranean - the Admiralty charts afford detailed cover of all waters, ports and harbours. These make up about 30 per cent of the total series. Modern charts in these areas usually have a source data diagram showing the sources from which the chart was compiled. The quantity and quality of the sources vary due to age and the part of the world the chart depicts. The other 70 per cent are derived from information on foreign charts, and the Admiralty versions are designed to provide charts for ocean passage and landfall, and approach and entry to the major ports. The series contains charts on many different scales, but can be divided very broadly as follows: Route planning 1:10 million Ocean planning 1:3.5 million Coast approach or landfall identification 1:1 million Coasting 1:300,000 to 1:200,000 Intricate or congested coastal waters 1:150,000 to 1:75,000 Port approach 1:50,000 or larger Terminal installation 1:12,500 or larger Charts on scales smaller than 1:50,000, except in polar regions, are on Mercator projection. Since 1978 all charts on 1:50,000 and larger have been produced on Transverse Mercator projection. Prior to 1978 larger scale charts were on a modified polyconic projection referred to as 'gnomonic', not to be confused with the true Gnomonic projection. Most of the detail shown on a chart consists of hydrographic information - soundings (selected spot depths) in metres (on older charts in fathoms or feet) reduced to a stated vertical datum; depth contours; dredged channels; and the nature of the seabed and foreshore. Features which present hazards to navigation, fishing and other marine operations are also shown. These include underwater rocks and reefs; wrecks and obstructions; submarine cables and pipelines and offshore installations. Shallow water areas are usually highlighted with pale blue tint(s). Also shown are aids established to assist the navigator - buoys, beacons, lights, fog signals and radio position finding and reporting services; and information about traffic separation schemes, anchorages, tides, tidal streams and magnetic variation. Outline coastal topography is shown especially objects of use as fixing marks. As a base for navigation the chart carries compass roses, scales, horizontal datum information, graduation (and sometimes land map grids), conversion tables and tables of tidal and tidal stream rates.

Admiralty Charts (2008) Catalogue of Admiralty Charts and other Hydrographic Publications NP131, UK Hydrographic Office

United Kingdom Hydrographic Office

Taunton
Somerset
TA1 2DN
United Kingdom