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waters and marginal land. Hydrography pertains to any waters.

Hydrography of streams will include information on the stream bed, flows[?], water quality[?] and surrounding land. Basin[?] or Interior Hydrography pays special attention to rivers and sweet water[?].

Hydrography on a large scale generally applies to the oceans and national or international efforts to describe them for navigational purposes. The science of oceanography is, in large part, a direct outgrowth of classical hydrography. In many respects the data are interchangeable, but marine hydrographic data will be particularly directed toward marine navigation and safety of that navigation.

Hydrographic measurements will include the tidal, current and wave information of physical oceanography. They will include bottom measurements, but with particular emphasis on those marine geological features that pose a hazard to navigation such as rocks, shoals, reefs and other features that obstruct ship passage. Unlike oceanography, hydrography will include shore features, natural and manmade, that aid in navigation. A Hydrographic survey will therefore include accurate positions and representations of hills, mountains and even lights and towers that will aid in fixing a ship's position as well as the aspects of the sea and seabed.

An interesting historical relationship is that of James Whistler (Arrangement in Grey and Black: Portrait of the Painter's Mother) to hydrography. His artistic talents were applied to the sometimes beautiful shore profiles that appeared on charts during his work as a cartographer with both the civilian and naval U. S. hydrographic organizations. Those profiles on early charts were etchings designed to aid mariners in identifying their landfall and harbor approaches.

Hydrography's origin lies in the making of chart like drawings and notations made by individual mariners. These were usually the private property, even closely held secrets, of individuals who used them for commercial or military advantage. Eventually organizations, particularly navies, realized the collection of this individualized knowledge and distribution to their members gave an organizational advantage. The next step was to organize members to actively collect information. Thus were born dedicated hydrographic organizations for the collection, organization, publication and distribution of hydrography incorporated into charts and sailing directions.

Oceanic hydrography may be considered a specialized subset of oceanography that is particularly dedicated to marine navigation and its safety. Hydrography, partly for reasons of safety, tends to be more traditional in outlook and has conventions that are not entirely "scientific" in some views. For example, hydrographic charts will usually tend to over represent least depths and ignore the actual submarine topography that will be portrayed on bathymetric charts. The former are the mariner's tools to avoid accident. The later are best representations of the actual seabed, as in a topographic map, for scientific and other purposes.

Hydrographic Organizations

Shipping organizations played a part, but the major players were the naval powers. Recognizing hydrographic information was a military advantage these naval organizations, usually under the direction of a "Hydrographer," utilized the expertise of naval officers in collecting hydrographic data that was incorporated into the navy's collection. In order to distribute the processed information (charts, directions, notices, and such) these organizations often developed specialized printing capabilities.

The first official organization, the French Depot des Cartes, Plans, Journaux et Memoirs Relatifs a la Navigation, was formed in 1720. The British, despite being active in hydrography, did not follow with official organization of the Hydrographic Department within the Admiralty until 1795. With that department the Royal Navy, while still relying on ordinary naval vessels and officers, organized the Royal Navy's Surveying Service with specially equipped and manned vessels.

In the United States two organizations were leaders in hydrography. The civilian Coast Survey was founded through an 1807 Congressional resolution and became the U.S. Coast and Geodetic Survey. That organization was eventually incorporated into the National Oceanic & Atmospheric Administration (NOAA (http://www.noaa.gov/)). The naval equivalent was started with the establishment of the Depot of Charts and Instruments in 1830 that by 1854 was designated the U.S. Naval Observatory and Hydrographical Office. The hydrographic portion became the U. S. Naval Hydrographic Office under the Hydrographer of the Navy. With the popularization of oceanography in the early 1960s (partly due to President Kennedy's interest) the name was changed to the U.S. Naval Oceanographic Office in 1962. That office, as a matter of historical and semantic interest, and the U.S. Naval Observatory are still part of the command overseen by the "Oceanographer of the Navy" with headquarters at the Naval Observatory.

Other countries were not so quick to rename their specialized navigational support agencies as "oceanographic" offices. The United Kingdom Hydrographic Office (UKHO (http://www.hydro.gov.uk/)) is now a part of the Ministry of Defence rather than a naval department. Australia's Australian Hydrographic Service and the International Hydrographic Organization (IHO (http://www.iho.shom.fr/)), an organization with some seventy member states working to standardize and improve hydrographic sciences, are examples.

See also : flood - drought - trasvasement - virtual water.

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