Hydrography

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Table of geography, hydrography, and navigation, from a 1728 Cyclopaedia. Table of Geography and Hydrography, Cyclopaedia, Volume 1.jpg
Table of geography, hydrography, and navigation, from a 1728 Cyclopaedia .

Hydrography is the branch of applied sciences which deals with the measurement and description of the physical features of oceans, seas, coastal areas, lakes and rivers, as well as with the prediction of their change over time, for the primary purpose of safety of navigation and in support of all other marine activities, including economic development, security and defence, scientific research, and environmental protection. [1]

Sea Large body of salt water

The sea, the world ocean or simply the ocean is the connected body of salty water that covers over 70% of Earth's surface. It moderates Earth's climate and has important roles in the water cycle, carbon cycle, and nitrogen cycle. It has been travelled and explored since ancient times, while the scientific study of the sea—oceanography—dates broadly from the voyages of Captain James Cook to explore the Pacific Ocean between 1768 and 1779. The word sea is also used to denote smaller, partly landlocked sections of the ocean and certain large, entirely landlocked, saltwater lakes, such as the Caspian Sea and the Dead Sea.

Lake A body of relatively still water, in a basin surrounded by land

A lake is an area filled with water, localized in a basin, surrounded by land, apart from any river or other outlet that serves to feed or drain the lake. Lakes lie on land and are not part of the ocean, and therefore are distinct from lagoons, and are also larger and deeper than ponds, though there are no official or scientific definitions. Lakes can be contrasted with rivers or streams, which are usually flowing. Most lakes are fed and drained by rivers and streams.

River Natural flowing watercourse

A river is a natural flowing watercourse, usually freshwater, flowing towards an ocean, sea, lake or another river. In some cases a river flows into the ground and becomes dry at the end of its course without reaching another body of water. Small rivers can be referred to using names such as stream, creek, brook, rivulet, and rill. There are no official definitions for the generic term river as applied to geographic features, although in some countries or communities a stream is defined by its size. Many names for small rivers are specific to geographic location; examples are "run" in some parts of the United States, "burn" in Scotland and northeast England, and "beck" in northern England. Sometimes a river is defined as being larger than a creek, but not always: the language is vague.

Contents

History

Alexander Dalrymple, the first Hydrographer of the Navy in the United Kingdom, appointed in 1795. Alexander Dalrymple AGE V07 1801.jpg
Alexander Dalrymple, the first Hydrographer of the Navy in the United Kingdom, appointed in 1795.

The origins of hydrography lay in the making of charts to aid navigation, by individual mariners as they navigated into new waters. These were usually the private property, even closely held secrets, of individuals who used them for commercial or military advantage. As transoceanic trade and exploration increased, hydrographic surveys started to be carried out as an exercise in their own right, and the commissioning of surveys was increasingly done by governments and special hydrographic offices. National organizations, particularly navies, realized that the collection, systematization and distribution of this knowledge gave it great organizational and military advantages. Thus were born dedicated national hydrographic organizations for the collection, organization, publication and distribution of hydrography incorporated into charts and sailing directions.

Commerce relates to "the exchange of goods and services, especially on a large scale". It includes legal, economic, political, social, cultural and technological systems that operate in a country or in international trade.

Military Organization primarily tasked with preparing for and conducting war

A military is a heavily-armed, highly organised force primarily intended for warfare, also known collectively as armed forces. It is typically officially authorized and maintained by a sovereign state, with its members identifiable by their distinct military uniform. It may consist of one or more military branches such as an Army, Navy, Air Force and in certain countries, Marines and Coast Guard. The main task of the military is usually defined as defence of the state and its interests against external armed threats.

Hydrographic survey Analysis of the topography of bodies of water, providing data for environmental, tidal calculations, maritime navigation and much more.

Hydrographic survey is the science of measurement and description of features which affect maritime navigation, marine construction, dredging, offshore oil exploration/offshore oil drilling and related activities. Strong emphasis is placed on soundings, shorelines, tides, currents, seabed and submerged obstructions that relate to the previously mentioned activities. The term hydrography is used synonymously to describe maritime cartography, which in the final stages of the hydrographic process uses the raw data collected through hydrographic survey into information usable by the end user.

Prior to the establishment of the United Kingdom Hydrographic Office, Royal Navy captains were responsible for the provision of their own charts. In practice this meant that ships often sailed with inadequate information for safe navigation, and that when new areas were surveyed, the data rarely reached all those who needed it. The Admiralty appointed Alexander Dalrymple as Hydrographer in 1795, with a remit to gather and distribute charts to HM Ships. Within a year existing charts from the previous two centuries had been collated, and the first catalogue published. [2] The first chart produced under the direction of the Admiralty, was a chart of Quiberon Bay in Brittany, and it appeared in 1800.

United Kingdom Hydrographic Office

The United Kingdom Hydrographic Office (UKHO) is the UK's agency for providing hydrographic and marine geospatial data to mariners and maritime organisations across the world. The UKHO is a trading fund of the Ministry of Defence (MoD) and is located in Taunton, Somerset, with a workforce of approximately 900 staff.

Royal Navy Maritime warfare branch of the United Kingdoms military

The Royal Navy (RN) is the United Kingdom's naval warfare force. Although warships were used by the English kings from the early medieval period, the first major maritime engagements were fought in the Hundred Years' War against the Kingdom of France. The modern Royal Navy traces its origins to the early 16th century; the oldest of the UK's armed services, it is known as the Senior Service.

Admiralty British Government ministry responsible for the Royal Navy until 1964

The Admiralty, originally known as the Office of the Admiralty and Marine Affairs, was the government department responsible for the command of the Royal Navy first in the Kingdom of England, later in the Kingdom of Great Britain, and from 1801 to 1964, the United Kingdom and former British Empire. Originally exercised by a single person, the Lord High Admiral (1385–1628), the Admiralty was, from the early 18th century onwards, almost invariably put "in commission" and exercised by the Lords Commissioners of the Admiralty, who sat on the Board of Admiralty.

Under Captain Thomas Hurd the department received its first professional guidelines, and the first catalogues were published and made available to the public and to other nations as well. In 1829, Rear-Admiral Sir Francis Beaufort, as Hydrographer, developed the eponymous Scale, and introduced the first official tide tables in 1833 and the first "Notices to Mariners" in 1834. The Hydrographic Office underwent steady expansion throughout the 19th century; by 1855, the Chart Catalogue listed 1,981 charts giving a definitive coverage over the entire world, and produced over 130,000 charts annually, of which about half were sold. [3]

Captain Thomas Hannaford Hurd was an officer of the Royal Navy, who rose to the rank of captain, becoming the second Admiralty hydrographer, a Superintendent of Chronometers and a Commissioner for the discovery of longitude. Hurd Peninsula is named after him due to his role in the discovery of Antarctica.

Francis Beaufort Irish hydrographer and naval officer

Rear Admiral Sir Francis Beaufort, KCB, FRS, FRGS, FRAS, MRIA was an Irish hydrographer and officer in the Royal Navy. Beaufort was the creator of the Beaufort Scale for indicating wind force.

Tide table Tabulated data used for tidal prediction which show the daily times and heights of high water and low water, usually for a particular location

Tide tables, sometimes called tide charts, are used for tidal prediction and show the daily times and levels of high and low tides, usually for a particular location. Tide heights at intermediate times can be approximated by using the rule of twelfths or more accurately calculated by using a published tidal curve for the location. Tide levels are typically given relative to a low-water vertical datum, e.g. the mean lower low water (MLLW) datum in the US.

The word hydrography comes from the Ancient Greek ὕδωρ (hydor), "water" and γράφω (graphō), "to write".

Ancient Greek Version of the Greek language used from roughly the 9th century BCE to the 6th century CE

The ancient Greek language includes the forms of Greek used in Ancient Greece and the ancient world from around the 9th century BCE to the 6th century CE. It is often roughly divided into the Archaic period, Classical period, and Hellenistic period. It is antedated in the second millennium BCE by Mycenaean Greek and succeeded by Medieval Greek.

Overview

Survey of the strategic port of Milford Haven produced by Lewis Morris in 1748 A plan of Milford Haven in the county of Pembroke south Wales.gif
Survey of the strategic port of Milford Haven produced by Lewis Morris in 1748

Large-scale hydrography is usually undertaken by national or international organizations which sponsor data collection through precise surveys and publish 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 focused on the search for hydrocarbons.

Hydrocarbon organic compound consisting entirely of hydrogen and carbon

In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons from which one hydrogen atom has been removed are functional groups called hydrocarbyls. Because carbon has 4 electrons in its outermost shell carbon has exactly four bonds to make, and is only stable if all 4 of these bonds are used.

Hydrographical measurements include the tidal, current and wave information of physical oceanography. They 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. 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. Therefore, a hydrographic survey may include the 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 physical aspects of the sea and seabed.

Hydrography, mostly for reasons of safety, adopted a number of conventions that have affected its portrayal of the data on nautical charts. 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 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 c. 2003–2005 have led to a narrowing of this difference, with many more hydrographic offices 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.

HMS Waterwitch, a hydrographic survey vessel HMS Waterwitch, formally Lancashire Witch.jpeg
HMS Waterwitch, a hydrographic survey vessel

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. A bathymetric chart does show marine topology accurately. Details covering the above limitations can be found in Part 1 of Bowditch's American Practical Navigator. 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 match today's GPS navigational accuracies. The hydrographic chart will use the best data available and will caveat its 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 descriptive requirements of the latter. Historically, this could include echosoundings 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 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 although if collected data is not for ship navigational uses, and is intended for scientific usage, it is more commonly called hydrometry or hydrology .

Hydrography of rivers and streams is also an integral part of water management. Most reservoirs in the United States use dedicated stream gauging and rating tables to determine inflows into the reservoir and outflows to irrigation districts, water municipalities and other users of captured water. River/stream hydrographers use handheld and bank mounted devices, to capture a sectional flow rate of moving water through a section and or current.

Organizations

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, supplying a wide 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 carried out since 1807 by the Office of Coast Survey of the National Oceanic and Atmospheric Administration within the U.S. Department of Commerce. [4]

See also

Related Research Articles

International Hydrographic Organization Intergovernmental organization

The International Hydrographic Organization (IHO) is an intergovernmental organization representing hydrography. In October 2019 the IHO comprised 93 Member States.

Oceanography The study of the physical and biological aspects of the ocean

Oceanography, also known as oceanology, is the study of the physical and biological aspects of the ocean. It is an important Earth science, which covers a wide range of topics, including ecosystem dynamics; ocean currents, waves, and geophysical fluid dynamics; plate tectonics and the geology of the sea floor; and fluxes of various chemical substances and physical properties within the ocean and across its boundaries. These diverse topics reflect multiple disciplines that oceanographers blend to further knowledge of the world ocean and understanding of processes within: astronomy, biology, chemistry, climatology, geography, geology, hydrology, meteorology and physics. Paleoceanography studies the history of the oceans in the geologic past.

Echo sounding Measuring the depth of water by transmitting sound waves into water and timing the return

Echo sounding is a type of sonar used to determine the depth of water by transmitting sound waves into water. The time interval between emission and return of a pulse is recorded, which is used to determine the depth of water along with the speed of sound in water at the time. This information is then typically used for navigation purposes or in order to obtain depths for charting purposes. Echo sounding can also refer to hydroacoustic "echo sounders" defined as active sound in water (sonar) used to study fish. Hydroacoustic assessments have traditionally employed mobile surveys from boats to evaluate fish biomass and spatial distributions. Conversely, fixed-location techniques use stationary transducers to monitor passing fish.

Nautical chart topographic map of a maritime area and adjacent coastal regions

A nautical chart is a graphic representation of a sea area and adjacent coastal regions. Depending on the scale of the chart, it may show depths of water and heights of land, natural features of the seabed, details of the coastline, navigational hazards, locations of natural and human-made aids to navigation, information on tides and currents, local details of the Earth's magnetic field, and human-made structures such as harbours, buildings and bridges. Nautical charts are essential tools for marine navigation; many countries require vessels, especially commercial ships, to carry them. Nautical charting may take the form of charts printed on paper or computerized electronic navigational charts. Recent technologies have made available paper charts which are printed "on demand" with cartographic data that has been downloaded to the commercial printing company as recently as the night before printing. With each daily download, critical data such as Local Notices to Mariners are added to the on-demand chart files so that these charts are up to date at the time of printing.

Bathymetric chart Map visually representing the submerged terrain

A bathymetric chart is the submerged equivalent of an above-water topographic map. Bathymetric charts are designed to present accurate, measurable description and visual presentation of the submerged terrain.

Canadian Hydrographic Service

The Canadian Hydrographic Service (CHS) is part of the federal department of Fisheries and Oceans Canada and is Canada's authoritative hydrographic office. The CHS represents Canada in the International Hydrographic Organization (IHO).

Bathymetry The study of underwater depth of lake or ocean floors

Bathymetry is the study of underwater depth of lake or ocean floors. In other words, bathymetry is the underwater equivalent to hypsometry or topography. The name comes from Greek βαθύς (bathus), "deep", and μέτρον (metron), "measure". Bathymetric charts are typically produced to support safety of surface or sub-surface navigation, and usually show seafloor relief or terrain as contour lines and selected depths (soundings), and typically also provide surface navigational information. Bathymetric maps may also use a Digital Terrain Model and artificial illumination techniques to illustrate the depths being portrayed. The global bathymetry is sometimes combined with topography data to yield a Global Relief Model. Paleobathymetry is the study of past underwater depths.

A research vessel is a ship or boat designed, modified, or equipped to carry out research at sea. Research vessels carry out a number of roles. Some of these roles can be combined into a single vessel but others require a dedicated vessel. Due to the demanding nature of the work, research vessels are often constructed around an icebreaker hull, allowing them to operate in polar waters.

Admiralty chart

Admiralty charts are nautical charts issued by the United Kingdom Hydrographic Office (UKHO) and subject to Crown Copyright. Over 3,500 Standard Nautical Charts (SNCs) and 14,000 Electronic Navigational Charts (ENCs) are available with the Admiralty portfolio offering the widest official coverage of international shipping routes and ports, in varying detail.

Chart datum The level of water from which depths displayed on a nautical chart are measured

A chart datum is the water level that depths displayed on a nautical chart are measured from. A chart datum is generally derived from some phase of the tide. Common chart datums are lowest astronomical tide and mean lower low water. In non-tidal areas, e.g. the Baltic Sea, mean sea level (MSL) is used.

The Danish Maritime Safety Administration (DaMSA) was a department of the Danish Ministry of Defence with administration located in Christianshavn, Copenhagen. DaMSA operated throughout Denmark as part of the Danish Search and Rescue (SAR) organization that runs 21 rescue stations located along the coasts of Denmark.

The Naval Oceanographic Office (NAVOCEANO), located at John C. Stennis Space Center in south Mississippi, comprises approximately 1,000 civilian, military and contract personnel responsible for providing oceanographic products and services to all elements within the Department of Defense.

The General Bathymetric Chart of the Oceans (GEBCO) is a publicly available bathymetric chart of the world's oceans. The project was conceived with the aim of preparing a global series of charts showing the general shape of the seafloor. Over the years it has become a reference map of the bathymetry of the world’s oceans for scientists and others.

The Naval Hydrographic and Oceanographic Service is a French public establishment of an administrative nature administered by the Ministry of Defence. It is the successor to the Dépôt des cartes et plans de la Marine, founded in 1720 which became the Naval Hydrographic Service in 1886 and the Naval and Oceanographic Service in 1971. Its present form was set up by decree number 2007-800 on 11 May 2007. Its board is presided over by the Chief of Staff of the French Navy and the body is directed by a director-general.

Hydrographer of the Navy

The Hydrographer of the Navy is the principal hydrographical Royal Naval appointment. From 1795 until 2001 the post was responsible for the production of charts for the Royal Navy, and around this post grew the United Kingdom Hydrographic Office. In 2001 the post was disassociated from UKHO, and the Hydrographer of the Navy is now a title bestowed upon the current Captain on the staff of Commodore, Devonport Flotilla.

World Hydrography Day, 21 June, was adopted by the International Hydrographic Organization as an annual celebration to publicise the work of hydrographers and the importance of hydrography.

Russian Hydrographic Service organization

The Russian Hydrographic Service, full current official name Department of Navigation and Oceanography of the Ministry of Defence of the Russian Federation, is Russia's hydrographic office, with responsibility to facilitate navigation, performing hydrographic surveys and publishing nautical charts.

Bathymetric attributed grid file format

Bathymetric Attributed Grid (BAG) is a file format designed to store and exchange bathymetric data.

References

  1. "International Hydrographic Organization".
  2. "The United Kingdom Hydrographic Office timeline" (PDF). UKHO. Archived from the original (PDF) on 2011-07-21. Retrieved 2011-01-23.
  3. "Charting the world for over 200 years". www.ukho.gov.uk. UKHO. Archived from the original on 2006-09-25. Retrieved 2006-11-15.
  4. "About Coast Survey".

Associations focussing on ocean hydrography

Associations focussing on river stream and lake hydrography