Hydrography is the measurement of the depths, the tides and currents of a body of water

Water

Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...

 and establishment of the sea

Sea

A sea generally refers to a large body of salt water, but the term is used in other contexts as well. Most commonly, it means a large expanse of saline water connected with an ocean, and is commonly used as a synonym for ocean...

, river or lake bed topography

Topography

Topography is the study of Earth's surface shape and features or those ofplanets, moons, and asteroids...

 and morphology

River morphology

The terms river morphology and its synonym fluvial geomorphology are used to describe the shapes of river channels and how they change over time...

. Normally and historically for the purpose of charting a body of water for the safe navigation

Navigation

Navigation is the process of monitoring and controlling the movement of a craft or vehicle from one place to another. It is also the term of art used for the specialized knowledge used by navigators to perform navigation tasks...

 of shipping. It includes the positioning and identification of things such as wreck

Wreck

Wreck may refer to:* Wreck, a ceremony of initiation into the 40 et 8 club* Wreck , an American indie rock band* A collision of an automobile, aircraft or other vehicle* Shipwreck, the remains of a ship after a crisis at sea...

s, reef

Reef

In nautical terminology, a reef is a rock, sandbar, or other feature lying beneath the surface of the water ....

s, structures (platforms etc), navigational lights, marks and buoy

Buoy

A buoy is a floating device that can have many different purposes. It can be anchored or allowed to drift. The word, of Old French or Middle Dutch origin, is now most commonly in UK English, although some orthoepists have traditionally prescribed the pronunciation...

s and coastline characteristics. It does not include water quality or composition (see Hydrology

Hydrology

Hydrology is the study of the movement, distribution, and quality of water on Earth and other planets, including the hydrologic cycle, water resources and environmental watershed sustainability...

).

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 hydrocarbon

Hydrocarbon

In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons from which one hydrogen atom has been removed are functional groups, called hydrocarbyls....

s.

Hydrographical measurements will include the tidal, current and wave

Wave

In physics, a wave is a disturbance that travels through space and time, accompanied by the transfer of energy.Waves travel and the wave motion transfers energy from one point to another, often with no permanent displacement of the particles of the medium—that is, with little or no associated mass...

 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, shoal

Shoal

Shoal, shoals or shoaling may mean:* Shoal, a sandbank or reef creating shallow water, especially where it forms a hazard to shipping* Shoal draught , of a boat with shallow draught which can pass over some shoals: see Draft...

s, reef

Reef

In nautical terminology, a reef is a rock, sandbar, or other feature lying beneath the surface of the water ....

s and other features that obstruct ship

Ship

Since the end of the age of sail a ship has been any large buoyant marine vessel. Ships are generally distinguished from boats based on size and cargo or passenger capacity. Ships are used on lakes, seas, and rivers for a variety of activities, such as the transport of people or goods, fishing,...

 passage. Bottom measurements also include collection of the nature of the bottom as it pertains to effective anchoring. Unlike oceanography, hydrography will include shore features, natural and manmade, that aid in navigation. A hydrographic survey

Hydrographic survey

Hydrographic survey is the science of measurement and description of features which affect maritime navigation, marine construction, dredging, offshore oil exploration/drilling and related disciplines. Strong emphasis is placed on soundings, shorelines, tides, currents, sea floor and submerged...

 will therefore include accurate positions and representations of hill

Hill

A hill is a landform that extends above the surrounding terrain. Hills often have a distinct summit, although in areas with scarp/dip topography a hill may refer to a particular section of flat terrain without a massive summit A hill is a landform that extends above the surrounding terrain. Hills...

s, mountain

Mountain

Image:Himalaya_annotated.jpg|thumb|right|The Himalayan mountain range with Mount Everestrect 58 14 160 49 Chomo Lonzorect 200 28 335 52 Makalurect 378 24 566 45 Mount Everestrect 188 581 920 656 Tibetan Plateaurect 250 406 340 427 Rong River...

s and even lights and tower

Tower

A tower is a tall structure, usually taller than it is wide, often by a significant margin. Towers are distinguished from masts by their lack of guy-wires....

s that will aid in fixing a ship's position as well as the aspects of the sea and seabed.

Hydrography, mostly for reasons of safety

Safety

Safety is the state of being "safe" , the condition of being protected against physical, social, spiritual, financial, political, emotional, occupational, psychological, educational or other types or consequences of failure, damage, error, accidents, harm or any other event which could be...

, had adopted a number of conventions that affect its portrayal of the data collected for nautical charting. For example, hydrographic charts are designed to portray what is safe for navigation, and therefore will usually tend to maintain least depths and occasionally de-emphasize the actual submarine topography

Topography

Topography is the study of Earth's surface shape and features or those ofplanets, moons, and asteroids...

 that would 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. Trends in hydrographic practice since ca. 2003-2005 have led to a narrowing of this difference, with many more hydrographic offices

Hydrographic office

A hydrographic office is an organization which is devoted to acquiring and publishing hydrographic information.Historically, the main tasks of hydrographic offices were the conduction of hydrographic surveys and the publication of nautical charts...

 maintaining "best observed" databases, and then making navigationally "safe" products as required. This has been coupled with a preference for multi-use surveys, so that the same data collected for nautical charting purposes can also be used for bathymetric portrayal.

Even though, in places, hydrographic survey data may be collected in sufficient detail to portray bottom topography in some areas, hydrographic charts only show depth information relevant for safe navigation and should not be considered as a product that accurately portrays the actual shape of the bottom. The soundings selected from the raw source depth data for placement on the nautical chart are selected for safe navigation and are biased to show predominately the shallowest depths that relate to safe navigation. For instance, if there is a deep area that can not be reached because it is surrounded by shallow water, the deep area may not be shown. The color filled areas that show different ranges of shallow water are not the equivalent of contours on a topographic map since they are often drawn seaward of the actual shallowest depth portrayed. The Bathymetric Chart on the other hand does show marine topology accurately. Details covering the above limitations can be found in Part 1 of Bowditch's American Practical Navigator

Bowditch's American Practical Navigator

The American Practical Navigator , originally written by Nathaniel Bowditch, is an encyclopedia of navigation. It serves as a valuable handbook on oceanography and meteorology, and contains useful tables and a maritime glossary...

. Another concept that affects safe navigation is the sparsity of detailed depth data from high resolution sonar systems. In more remote areas, the only available depth information has been collected with lead lines. This collection method drops a weighted line to the bottom at intervals and records the depth, often from a rowboat or sail boat. There is no data between soundings or between sounding lines to guarantee that there is not a hazard such as a wreck or a coral head waiting there to ruin a sailor's day. Often, the navigation of the collecting boat does not meet today's GPS navigational accuracies. The hydrographic chart will use the best data available and will caveat it's nature in a caution note or in the legend of the chart.

A hydrographic survey is quite different from a bathymetric survey in some important respects, particularly in a bias toward least depths due to the safety requirements of the former and geomorphologic

Geomorphology

Geomorphology is the scientific study of landforms and the processes that shape them...

 descriptive requirements of the latter. Historically, this could include echosoundings

Echo sounding

Echo sounding is the technique of using sound pulses directed from the surface or from a submarine vertically down to measure the distance to the bottom by means of sound waves. This information is then typically used for navigation purposes or in order to obtain depths for charting purposes...

 being conducted under settings biased toward least depths, but in modern practice hydrographic surveys typically attempt to best measure the depths observed, with the adjustments for navigational safety being applied after the fact.

Hydrography of stream

Stream

A stream is a body of water with a current, confined within a bed and stream banks. Depending on its locale or certain characteristics, a stream may be referred to as a branch, brook, beck, burn, creek, "crick", gill , kill, lick, rill, river, syke, bayou, rivulet, streamage, wash, run or...

s will include information on the stream bed, flow

Environmental flow

‘’’Environmental flows’’’ describe the quantity, timing, and quality of water flows required to sustain freshwater and estuarine ecosystems and the human livelihoods and well being that depend on these ecosystems...

s, water quality

Water quality

Water quality is the physical, chemical and biological characteristics of water. It is a measure of the condition of water relative to the requirements of one or more biotic species and or to any human need or purpose. It is most frequently used by reference to a set of standards against which...

 and surrounding land. Basin

Drainage basin

A drainage basin is an extent or an area of land where surface water from rain and melting snow or ice converges to a single point, usually the exit of the basin, where the waters join another waterbody, such as a river, lake, reservoir, estuary, wetland, sea, or ocean...

 or Interior Hydrography pays special attention to rivers and potable water  although if collected data is not for ship navigational uses, and is intended for scientific useage it is more commonly called Hydrology

Hydrology

Hydrology is the study of the movement, distribution, and quality of water on Earth and other planets, including the hydrologic cycle, water resources and environmental watershed sustainability...

.

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

Commerce

While business refers to the value-creating activities of an organization for profit, commerce means the whole system of an economy that constitutes an environment for business. The system includes legal, economic, political, social, cultural, and technological systems that are in operation in any...

 or military

Military

A military is an organization authorized by its greater society to use lethal force, usually including use of weapons, in defending its country by combating actual or perceived threats. The military may have additional functions of use to its greater society, such as advancing a political agenda e.g...

 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

James McNeill Whistler

James Abbott McNeill Whistler was an American-born, British-based artist. Averse to sentimentality and moral allusion in painting, he was a leading proponent of the credo "art for art's sake". His famous signature for his paintings was in the shape of a stylized butterfly possessing a long stinger...

 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

Harbor

A harbor or harbour , or haven, is a place where ships, boats, and barges can seek shelter from stormy weather, or else are stored for future use. Harbors can be natural or artificial...

 approaches. (An interesting account of his brief career with hydrographic charting can be found at: http://www.lib.noaa.gov/noaainfo/heritage/coastsurveyvol1/BACHE7.html.)

Organisations

Hydrographic services in most countries are carried out by specialised hydrographic office

Hydrographic office

A hydrographic office is an organization which is devoted to acquiring and publishing hydrographic information.Historically, the main tasks of hydrographic offices were the conduction of hydrographic surveys and the publication of nautical charts...

s. The international coordination of hydrographic efforts lies with the International Hydrographic Organization

International Hydrographic Organization

The International Hydrographic Organization is the inter-governmental organisation representing the hydrographic community. It enjoys observer status at the UN and is the recognised competent authority on hydrographic surveying and nautical charting...

.

The United Kingdom Hydrographic Office

United Kingdom Hydrographic Office

The United Kingdom Hydrographic Office is an organisation within the UK government responsible for providing navigational and other hydrographic information for national, civil and defence requirements...

 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. In the United States, the hydrographic charting function has been subsumed into the National Geospatial-Intelligence Agency

National Geospatial-Intelligence Agency

The National Geospatial-Intelligence Agency is an agency of the federal government of the United States with the primary mission of collecting, analyzing and distributing geospatial intelligence in support of national security. NGA was formerly known as the National Imagery and Mapping Agency ...

 (NGA).

See also

• Hydrographic survey
  Hydrographic survey
  Hydrographic survey is the science of measurement and description of features which affect maritime navigation, marine construction, dredging, offshore oil exploration/drilling and related disciplines. Strong emphasis is placed on soundings, shorelines, tides, currents, sea floor and submerged...
  
  
• Bathymetric chart
• Cartography
  Cartography
  Cartography is the study and practice of making maps. Combining science, aesthetics, and technique, cartography builds on the premise that reality can be modeled in ways that communicate spatial information effectively.The fundamental problems of traditional cartography are to:*Set the map's...
  
  
• Coastal geography
  Coastal geography
  Coastal geography is the study of the dynamic interface between the ocean and the land, incorporating both the physical geography and the human geography of the coast...
  
  
• Drought
  Drought
  A drought is an extended period of months or years when a region notes a deficiency in its water supply. Generally, this occurs when a region receives consistently below average precipitation. It can have a substantial impact on the ecosystem and agriculture of the affected region...
  
  
• Evapotranspiration
  Evapotranspiration
  Evapotranspiration is a term used to describe the sum of evaporation and plant transpiration from the Earth's land surface to atmosphere. Evaporation accounts for the movement of water to the air from sources such as the soil, canopy interception, and waterbodies...
  
  
• Flood
  Flood
  A flood is an overflow of an expanse of water that submerges land. The EU Floods directive defines a flood as a temporary covering by water of land not normally covered by water...
  
  
• Hydrology
  Hydrology
  Hydrology is the study of the movement, distribution, and quality of water on Earth and other planets, including the hydrologic cycle, water resources and environmental watershed sustainability...
  
  
• Hydrologic cycle
• Hydrometeorology
  Hydrometeorology
  Hydrometeorology is a branch of meteorology and hydrology that studies the transfer of water and energy between the land surface and the lower atmosphere....
  
  
• Hydrometry
  Hydrometry
  Hydrometry is the monitoring of the components of the hydrological cycle including rainfall, groundwater characteristics, as well as water quality and flow characteristics of surface waters...
  
  
• Trasvasement
• Virtual water
  Virtual water
  Virtual water refers, in the context of trade, to the water used in the production of a good or service. For instance, it takes 1,300 cubic meters of water on average to produce one metric tonne of wheat. The precise volume can be more or less depending on climatic conditions and agricultural...
  
  
• Pierre Desceliers
  Pierre Desceliers
  Pierre Desceliers was a French cartographer of the Renaissance and an eminent member of the Dieppe School of Cartography. He is considered the father of French hydrography....
  
  

External links

• The International Hydrographic Organization- is an intergovernmental consultative and technical organization that was established in 1921 to support safety of navigation and the protection of the marine environment.
• The Academy Of Positioning Marine And Bathymetry (APOMAB)- is an independent, no-profit, no-governmental. It provides a forum for all those involved in activities related to the disciplines of marine positioning and bathymetry members who live or work anywhere in the world.
• International Federation of Hydrographic Societies (formerly The Hydrographic Society)