Everything about Hydrographic totally explained
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
oceanography and
limnology are subsets of hydrography. In
specialized usage the term applies to those measurements and descriptions of
navigable waters necessary for safe
navigation of
vessels.
Overview
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
hydrocarbons.
Hydrographical measurements will include the
tidal,
current and
wave information 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
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.
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 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 that'll 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.
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
potable water.
History
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.
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
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.
Organisations
Hydrographic services in most countries are carried out by specialised
hydrographic offices. The international coordination of hydrographic efforts lies with the
International Hydrographic Organization.
The
United Kingdom Hydrographic Office is 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.
Further Information
Get more info on 'Hydrographic'.
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