Hydrography focuses on the measurement of physical characteristics of
waters and marginal land. In the "generalized usage", "hydrography" pertains to measurement and description of any waters. With that usage oceanographyand limnologyare subsets of hydrography. In "specialized usage" the term applies to those measurements and descriptions of navigablewaters necessary for safe navigationof vessels.
Large scale hydrography is usually undertaken by national or international organizations that sponsor data collection through precise surveys and the publication of charts and descriptive material for navigational purposes. The science of oceanography is, in part, an 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. Marine resource exploration and exploitation is a significant application of hydrography, principally focussed on the search for
Hydrographical measurements will include the tidal, current and
waveinformation of physical oceanography. They will include bottom measurements, with particular emphasis on those marine geographical features that pose a hazard to navigation such as rocks, shoals, reefs and other features that obstruct shippassage. Unlike oceanography, hydrography will include shore features, natural and manmade, that aid in navigation. A hydrographic surveywill 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.
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 topographythat will be portrayed on bathymetric charts. The former are the mariner's tools to avoid accident. The latter are best representations of the actual seabed, as in a topographic map, for scientific and other purposes.
A hydrographic survey is quite different from a bathymetric survey in some important respects, particularly in a bias toward least depths, because of the safety requirements of the former and geomorphologic descriptive requirements of the latter. As just one important example the echosoundings will be conducted under settings biased toward least depths while in bathymetric surveys they will be set for best description of the submarine topographical features that may include sound velocity and slope corrections that are more accurate but eliminate the safety bias.
streams will include information on the stream bed, flows, water qualityand surrounding land. Basin or "Interior Hydrography" pays special attention to riversand potable water.
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
militaryadvantage. 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.
An interesting historical relationship is that of James Whistler to hydrography. His artistic talents were applied to the sometimes beautiful shore profiles that appeared on charts during his work as a
cartographerwith 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 harborapproaches.
Hydrographic services in most countries are carried out by specialised
hydrographic offices. The international coordination of hydrographic efforts lies with the International Hydrographic Organization.
United Kingdom Hydrographic Officeis one of the oldest and most respected hydrography organisations in the world, supplying the widest range of charts covering the globe to other countries, allied military organisations and the public.
* [http://www.ukho.gov.uk United Kingdom Hydrographic Office] - an executive agency of the UK's Ministry of Defence.
* [http://www.hydrographicsociety.org International Federation of Hydrographic Societies (formerly The Hydrographic Society)]
* [http://www.uky.edu/KGS/gis/kydrain.htm Hydrography of Kentucky]
* [http://sun1.giac.montana.edu/gyadc/metadata/grtehydr.html Hydrography of Grand Teton National Park] and surrounding area
* [http://www.regione.abruzzo.it/turismo/en/territorio/hydrography.htm The hydrography of an Italian region]
* [http://www.dhyg.de/joomla/index.php German Hydrographic Society]
* [http://chartmaker.ncd.noaa.gov/hsd/hydrog.htm NOAA Hydrography and coastal surveys]
* [http://nhd.usgs.gov/ USGS National hydrographical dataset]
* [http://www.hcu-hamburg.de/geomatik/department/department.htm HafenCity Universität Hamburg Department Geomatik]
* [http://www.hydrobharat.nic.in Indian Hydrography
* [http://www.ccom.unh.edu The Center For Coastal and Ocean Mapping - Joint Hydrographic Center]
* [http://www.charts.gc.ca Canadian Hydrographic Service]
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