Hydrography document
Download as DOCX, PDF1 like211 views
The International Hydrographic Organization (IHO) was established in 1921 to support safety of navigation and protect the marine environment. It coordinates activities between national hydrographic offices to promote standardization and sharing of hydrographic data. The IHO develops standards for hydrographic and nautical charting used by its 85 member countries. It directs programs like the General Bathymetric Chart of the Oceans in partnership with the Intergovernmental Oceanographic Commission.
Hydrography document
- 1. IHO 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 object of the Organization is to bring about: 1.The coordination of the activities of national hydrographic offices 2.The greatest possible uniformity in nautical charts and documents 3.The adoption of reliable and efficient methods of carrying out and exploiting hydrographic surveys 4. The development of the sciencesin the field of hydrography and the techniques employed in descriptive oceanography The official representative of each Member Government within the IHO is normally the national Hydrographer, or Director of Hydrography, who, together with their technical staff, meet at 3-yearly intervals in Monaco for an IHO Assembly. The Assembly reviews the progress achieved by the Organization through its committees, sub committees and working groups, and adopts the programmes to be pursued during the ensuing 3-year period. A Secretary General and two Directors are elected to administer the work of the Organization during that time. The Secretary General and Directors, together with a small international staff of technical experts in hydrography and nautical cartography and locally recruited administrative support staff make up the IHO Secretariat in Monaco. The Secretariat of the IHO, coordinates and promotes the IHO's programmes and provides advice and assistance to Member States and others. History Formation of the International Hydrographic Bureau. International cooperation in the field of hydrography began with the first International Maritime Conference held in Washington in 1889, followed by two others in Saint Petersburg,in 1908 and 1912. In 1919, twenty-four nations met in London for a Hydrographic Conference,during which it wasdecided that a permanent body should be created. The resulting International Hydrographic Bureau began its activity in 1921 with eighteen Member States (including the British Empire then composed of the United Kingdom and Australia). At the invitation of H.S.H. Prince Albert I of Monaco, a noted marine scientist, the Bureau was provided with headquarters in the Principality of Monaco. The Organization has remained in Monaco ever since, thanks to the continuing and very generous support of the Prince's successors. During the 19th century, many maritime nations established hydrographic offices to provide means for improving the navigation of naval and merchant vessels by providing nautical publications, nautical charts, and other navigational services. There were substantial differences in hydrographic procedures charts, and publications. In 1889, an International Maritime Conference was held at Washington, D.C.,and it was proposed to establish a "permanent international commission." Similar proposals were made at the sessions of the International Congress of Navigation held at Saint Petersburg in 1908 and the International Maritime Conference held at Saint Petersburg in 1912. In 1919 the hydrographers of Great Britain and France cooperated in taking the necessary steps to convene an international conference of hydrographers. London was selected as the most suitable place for this conference,and on 24 July 1919, the First International Conference opened, attended by the hydrographers of 24 nations. Functions The IHO develops hydrographic and nautical charting standards. These standards are subsequently adopted and used by its 85 member countries and others in their surveys, nautical charts, and publications. The almost universal use of the IHO standards means that the products and services provided by the world's national hydrographic and oceanographic offices are consistent and recognizable by all seafarers and for other users. Much has been done in the field of standardization since the Bureau (now the IHO) was founded. The IHO has encouraged the formation of Regional Hydrographic Commissions (RHCs). Each RHC coordinates the national surveying and charting activities of countries within each region and acts as a forum to address other matters of common hydrographic interest. The 15 RHCs plus the IHO Hydrographic Commission on Antarctica (HCA) effectively cover the world.The IHO,in partnership with the Intergovernmental Oceanographic Commission (IOC),directs the GeneralBathymetric Chart of the Oceansprogramme. . Types of hydrography 1. Navigational hydrography : 2. Offshore hydrography : 3. Oceanic hydrography : Horizontal Controls: In an extensive survey, the primary horizontal control is established primarily by running theodolite and tape traverse before the triangulation station. The traverse lines being run to following the shore lines approximately. In survey of less extent the primary horizontal control only is required and is established by running a theodolite
- 2. and tape traverse sufficiently close to shore line. For rough work, the control may be established by running a theodolite and staid traverse or plane table trader. Vertical Controls: These are based upon a series of bench marks established near the shore line by spirit leveling and these serve for setting and checking tide gages etc to which the sounding are referred. Uses for Bathymetry maps and data 1. Sustainable Resource Management: a. Fisheries, Fisheries enhancement, Aquaculture b. Identify spawning grounds both to aid the fishing industry and to institute and enforce conservation regulations to protect that industry in perpetuity. c. (seabed character, hazards to gear, damage to habitats) d. Petroleum & Minerals e. Exploration for hydrocarbons both to aid and regulate exploration. f. Geological modeling of ocean basin evolution, geological and tectonic processes. 2. Environmental Stewardship: a. Habitat Monitoring, Land Use Planning, Environmental Quality, National Heritage, Marine Protected Areas. b. assessing the impact of coastal sediment transport and pollution, c. offshore waste disposal; baseline monitoring d. Planetary scale global observing systems ( e.g. GOOS, the Global Ocean Observing System, and GCOS, the Global Climate Observing System) e. distribution of chemical products, harmful or not, in the deep ocean), 3. Health & Safety: a. Sewage sites, Dredge spoils disposal, Risk Reduction, Oil Spill Readiness Plans, Coastal Planning/Global Warming Sea Level Rise, Hazard Mitigation (Earthquakes; Storm Surge & Tsunami; Seafloor Hazards) Accident investigation b. Most pollutants eventually end up in the ocean, and the ocean cannot be considered an infinitely large sink into which we can forever dump wastes. c. predictions of the future patterns of climate change on time scales of months to decades 4. Infrastructure: a. Cables & Pipeline, Offshore Exploration & Production Platforms, Coastal Structures, Dredging, Opening Northwest Passage b. transport (ports, harbors, navigational hazards c. oil platform sitting 5. Sovereignty: a. Boundaries definition, Juridical Continental Shelf under the UNCLOS, Seabed Surveillance & Intervention, Contraband & Drugs b. Marine Cadaster c. Seabed Surveillance & Intervention, Contraband & Drugs d. Assisting the International Seabed Authority to manage the deep oceans 6. Coastal Engineering Coastalengineering could be defined asthe technology required to measure describe or quantify the physical properties, processes and changes in the coastal zone. Most numerical models used for modeling the coastal zone require wave refraction information and this cannot be known without bathymetric information. Refraction is the bending of waves due to the variation in water depths. The part of a wave in shallow water moves slower than the part of a wave in deeper water. So when the depth under a wave crest varies along the crest, the wave bends (refracts). 7. Fundamental Science a. Contributes to most other marine sciences b. Valuable in the education of all marine scientists c. climate Speed of Sound Sound travels about 1500 meters per second in seawater. Sound travels much more slowly in air, at about 340 meters per second. The speed of sound in seawater is not a constant value. It varies by a small amount (a few percent) from place to place, season to season,morning to evening, and with water depth. Although the variations in the speed of
- 3. sound are not large, they have important effects on how sound travels in the ocean. Sound speed is affected by the oceanographic variables of temperature,salinity,and pressure. The speed of sound in water increases with increasing water temperature,increasing salinity and increasing pressure (depth). The approximate change in the speed of sound with a change in each property is:  Temperature 1°C = 4.0 m/s  Salinity 1PSU = 1.4 m/s  Depth (pressure) 1km = 17 m/s Methods ofspeed ofsound determination The sound velocity determination in water is one of the important issue in hydrographic surveying and should be determined precisely to obtain correct depth. It may be determined mainly with different methods and using different instruments as follows (de Jong et al. 2002, USAGE 2002); a-) from empirical formulas with the information from CTD (Conductivity, Temperature, and Depth) sensor -or probe b-) with bathythermograph c-) with velocity meter d-) by bar check calibration. e-) velocity meter Sound Velocity Determination with Empirical Formulas (equations) The value of sound velocity, c, could be determined by means of empirical formulae using the temperature T, pressure P (or depth D) and salinity S measured by CTD sensor. There are Number of formulae available to calculate the sound velocity in water given in literature such as Wilson (1960), Chen and Millero (1977), DelGrosso (1974), Mackenzie (1981), Medwin (1975). Pike and Beiboer, (1993) made an extensive comparison of several algorithms and they suggested the following order of preference: 1- ) Chen & Millero (only for water depths less than 1000 m) 2- ) Del Grosso (only for water depths greater than 1000 m) 3- ) Mackenzie (for rapid computations in oceanic waters to 8000 m water depth) 4- ) Medwin (for rapid computations in oceanic waters to 1000 m water depth). 1: the scope of hydrography in marine research Role of sound velocity in data collection 2: basic principles of hydrographic survey
- 4. Principles of cartography and projections 3: the importance of ocean and coastal mapping 4: define 5: survey standard, Error: The difference between an observed or computed value of a quantity and the ideal or true value of that quantity Accuracy: The extent to which a measured or enumerated value agrees with the assumed or accepted value Precision:The degree of refinement of a value not to be confused with ACCURACY,which is the degree of conformance with the correct value. Uncertainty:Uncertainty is a situation which involves imperfect and/or unknown information. Resolution:The separation by an optical system of parts of an object or of two or more objects close together. The degree of ability to make such a separation, called resolving power, is expressed as the minimum distance between two objects that can be separated. Attention: Reflection:The process whereby a surface of discontinuity turns back a portion of the incident radiation into the medium through which the radiation approached. Refraction:The process in which the direction of energy propagation is changed as the result of a change in density within the propagating medium, or as the energy passes through the interface representing a density discontinuity between two media. Datums Are the basis for all geodetic survey work. Datum is a base elevation used as a reference from which to reckon heights or depths. A tidal datum is a standard elevation defined by a certain phase of the tide. Tidal datums are used as references to measure local water levels and should not be extended into areas having differing oceanographic characteristics without substantiating measurements. In order that they may be recovered when needed, such datums are referenced to fixed points known as bench marks. Tidal datums are also the basis for establishing privately owned land, state owned land, territorial sea, exclusive economic zone, and high seas boundaries. Chart Datum is also the level to which tidal levels and predictions are measured and is the same as the zero of the tidal predictions. There are two main datums. Horizontal datums measure positions (latitude and longitude) on the surface of the Earth, while vertical datums are used to measure land elevations and water depths. Methods of horizontal and vertical control 1: triangulation 2: trilateration 3: mixed methods a. Traverse b. Not oriented open traverse c. Oriented open traverse d. Not oriented closed traverse 4: photogrammetry method a. aerophotogrammetry 5: intervisibility of geodetic stations Vertical methods 1: geometric leveling
- 5. 2: trigonometric levelling 3: altimetry with GPS 6: influence of coastal processes on hydrographic survey Geodetic distance is the shortest distance Bathymetry is a great lie Metadata Metadata is structured information that describes, explains, locates, or otherwise makes it easier to retrieve, use, or manage an information resource. Metadata is often called data about data or information about information. There are three main types of metadata: 1. Descriptive metadata describes a resource for purposes such as discovery and identification. It can include elements such as title, abstract, author, and keywords. 2. Structural metadata indicates how compound objects are put together, for example, how pages are ordered to form chapters. 3. Administrative metadata provides information to help manage a resource,such as when and how it was created,file type and other technical information, and who can access it. There are severalsubsets of administrative data; two that are sometimes listed as separate metadata types are: a. Rights management metadata, which deals with intellectual property rights. b. Preservation metadata, which contains information needed to archive and preserve a resource. Metadata functions ď‚· Resource discovery 1. Allowing resources to be found by relevant criteria; 2. Identifying resources; 3. Bringing similar resources together; 4. Distinguishing dissimilar resources; 5. Giving location information. ď‚· Organizing e-resources 1. Organizing links to resources based on audience or topic. 2. Building these pages dynamically from metadata stored in databases. ď‚· Facilitating interoperability 1. Using defined metadata schemes,shared transfer protocols, and crosswalks between schemes, resources across the network can be searched more seamlessly. I. Cross-system search,e.g.,using Z39.50 protocol; II. Metadata harvesting, e.g.,OAI protocol. ď‚· Digital identification 1. Elements for standard numbers, e.g., ISBN 2. The location of a digital object may also be given using: I. a file name II. a URL III. some persistent identifiers, e.g., PURL (Persistent URL); DOI (Digital Object Identifier) 3. Combined metadata to act as a set of identifying data, differentiating one object from another for validation purposes. ď‚· Archiving and preservation 1. Challenges: I. Digital information is fragile and can be corrupted or altered; II. It may become unusable as storage technologies change. 2. Metadata is key to ensuring that resources will survive and continue to be accessible into the future. Archiving and preservation require special elements: I. to track the lineage of a digital object, II. to detail its physical characteristics, and III. To document its behavior in order to emulate it in future technologies.
- 6. Transducer A transducer is a device that converts one form of energy to another. Usually a transducer converts a signal in one form of energy to a signal in another. Transducers are often employed at the boundaries of automation, measurement, and control systems, where electrical signals are converted to and from other physical quantities (energy, force, torque, light, motion, position, etc.). The process of converting one form of energy to another is known as transduction. Types 1.Passive: Passive sensors require an externalpower source to operate, which is called an excitation signal. The signal is modulated by the sensor to produce an output signal. 2. Active:Active sensors generate electric signals in response to an external stimulus without the need of an additional energy source. Such examples are a thermocouple, photodiode, and a piezoelectric sensor. 3. Sensor: A sensor is a device that receives and responds to a signal or stimulus. A transducer is a term that can be used for the definition of many devices such as sensors,actuators, or transistors. 4. Actuators: An actuator is a device that is responsible for moving or controlling a mechanism or system. It is operated by a source of energy, which can be mechanical force, electrical current, hydraulic fluid pressure,or pneumatic pressure,and converts that energy into motion. An actuator is the mechanism by which a control system acts upon an environment. The control system can be simple (a fixed mechanical or electronic system), software-based (e.g. a printer driver, robot control system), a human, or any other input. Bidirectional : Bidirectional transducers convert physical phenomena to electrical signals and also convert electrical signals into physical phenomena. Generate electrical power if the motor shaft is turned by an external torque. Ideal characteristics High dynamic range  High repeatability  Low noise  Low hysteresis Applications Transducers are used in electronic communications systems to convert signals of various physical forms to electronic signals, and vice versa Electromagnetic:  Hall effect sensors – converts a magnetic field level into an electrical signal  Electrochemical:  pH probes  Electro-galvanic fuel cells  Hydrogen sensors  Electromechanical (electromechanical output devices are generically called actuators):  Accelerometers  Air flow sensors
- 7.  Potentiometers (when used for measuring position)  Pressure sensors  Vibration powered generators  Electroacoustic:  Geophones – converts a ground movement (displacement) into voltage (vibrations → motion of conductor/coil → magnetic field → signal)  Gramophone pickups – (air pressure → motion → magnetic field → electrical signal)  Hydrophones – converts changes in water pressure into an electrical signal  Sonar transponders (water pressure → motion of conductor/coil → magnetic field → electrical signal)  Ultrasonic transceivers,transmitting ultrasound (transduced from electricity) as well as receiving it after sound reflection from target objects, availing for imaging of those objects.  Electro-optical (Photoelectric):  Fluorescent lamps – converts electrical power into incoherent light  Light-emitting diodes – converts electrical power into incoherent light  Laser diodes – converts electrical power into coherent light  Photodiodes, photoresistors, phototransistors, photomultipliers – converts changing light levels into electrical signals Thermoelectric:  Resistance temperature detectors (RTD) – converts temperature into an electrical resistance signal  Thermocouples – converts relative temperatures of metallic junctions to electrical voltage  Thermistors (includes PTC resistor and NTC resistor)  Radioacoustic:  Radio receiver’s converts electromagnetic transmissions to electrical signals.  Radio transmitters’ converts electrical signals to electromagnetic transmissions. WGS84 The World Geodetic System (WGS) is a standard for use in cartography, geodesy, and navigation including GPS. It comprises a standard coordinate system for the Earth, a standard spheroidal reference surface (the datum or reference ellipsoid) for raw altitude data, and a gravitational equipotential surface (the geoid) that defines the nominal sea level. The latest revision is WGS 84 (WGS 1984, EPSG: 4326), established in 1984 and last revised in 2004.Earlier schemes included WGS 72, WGS 66, and WGS 60. WGS 84 is the reference coordinate system used by the Global Positioning System. IHO The law of the sea The law of the sea is a body of customs, treaties, and international agreements by which governments maintain order, productivity, and peaceful relations on the sea. Theodolite Contour line Geodesy Vertical and horizontal positioning
- 8. Role of vertical datum in ocean depth measurement The errors and uncertainty associated with hydrographic survey The importance of ocean and coastal mapping Bathymetric data is important for producing navigation products (such as nautical charts) and for the advancement of many important Earth sciences. For example, a detailed knowledge of global bathymetry is a prerequisite for mapping the oceans and for understanding how the earth’s global systems interact. The shape of the ocean basins, ridges and mountains influence the flow of sea water carrying heat, salt, nutrients, and pollutants. They also influence the propagation of energy from undersea seismic events that result in potential disasters such as tsunamis. Although 71 % of the Earth surface is covered by water, the world´s oceans remain poorly mapped. Seafloor classification How can you classify seafloor in vicinity of continental shelf region? Characterize of a sea mountain IHO Coastal protection Bathymetry mapping tools Bathymetry map and navigational chart comparison Navigation Charts are carefully constructed instruments designed to provide a basis for safely locating a vessel in relationship to the physical geography of an area at sea,and providing information that can affect the movement of the vessel. To do so, a Navigation Chart must: (1) Form the base for the graphical exercise of charting; (2) Provide information on the nature and position of navigational hazards; and (3) Provide information on the identification and characteristics of navigational aids. A bathymetry map is not constrained by the need to protect mariners and their vessels. The aim of the bathymetric map is to show every “nook and cranny” of the sea floor in the best possible way permitted by the data available and the horizontal scale of the map. Bathymetry and hydrography of Bay of Bengal Vertical datum The elevation of a point can only be expressed with to the elevation of another point.it could be related to the center of the earth,the mean surface of the ocean,the orbit of a satellite or simply a bench mark. The chosen reference to which elevations are referred to is called a vertical datum. Currently there are about 100-200 vertical datums in the world. Orthometric heights are defined with respect to the geoid which is an equipotential surface approximately by mean sea level.