Hydrography
The hydrographic or hydrographic concerned with the measurement of the form of rivers, sea and the seabed (hydrographic, water measurement). It is therefore part of geomatics ( geodesy and geoinformatics ). The survey includes the acquisition, evaluation, modeling and presentation of the morphology, the nature and shape of the soil. The actual field of activity is more varied.
In Austria there is a different conception of hydrography. It is assigned to hydrology here. The fields of activity do not entirely coincide with the importance of hydrography in Germany (or hydrography international), so the Austrian perspective is also discussed here: Hydrography (geographic hydrology) describes the teaching of manifestations, properties, occurrences, Distribution and household of water above, on and below the surface of the earth. Hydrography is a part of geography as well as geophysics . Its branches are hydrology ( limnology ) with its sub-area river science ( potamology ), spring and groundwater science ( hydrogeology ), oceanography (marine science) and the theory of bed load movement and scree movement in rivers and on coasts. The water of the open seas deals with oceanography, that of the glacier with glaciation ( glaciology ). This description largely coincides with that of hydrology .
Definitions
UNESCO and DIN definition
Hydrography is "the science and practice of measuring and displaying the parameters necessary to describe the nature and shape of the bottom of the water, its relationship to the land and the state and dynamics of the water." (United definition Nations Economic and Social Council, 1978)
This definition is also recorded in DIN 18709-3. In DIN, the terms water surveying, lake surveying and inland water surveying are uniformly translated into English with "hydrographic surveying".
English IHO definition
The International Hydrographic Organization (IHO) defines "Hydrography" as follows:
That branch of applied sciences which deals with the measurement and description of the features of the seas and coastal areas for the primary purpose of navigation and all other marine purposes and activities - inter alia - offshore activities, research, protection of the environment, and prediction services.
A new definition of "hydrography" is currently being discussed in the IHO (April, 2009).
Austrian ÖNORM definition
Hydrography is that part of hydrology that deals with the quantitative recording and description of the water cycle on, below and above the surface of the earth and with the treatment of related issues. (Supplementary ÖNORM B 2400 to ÖNORM EN ISO 772)
This definition, well known in Austria and Switzerland, is unusual in Germany and does not match the meaning of the English word "hydrography".
Tasks of hydrography
The results of the measurements are mostly sea charts or geo-referenced, digital 3-D models.
71% of the earth is covered with water. Science has mapped the surface of the planet Mars better than the ground below the surface of the water. The main tasks of hydrography are the recording of the nature and the shape of the ground under water
- to ensure the safety and ease of shipping
- for planning and monitoring measurements for coastal protection
- for the monitoring of water bodies (sedimentation, condition)
- for (construction) engineering applications (pipeline, wind turbines, bridge construction)
- for exploration purposes (resources from the sea ...)
- for (underwater) archeology (wreck search, remains of settlements under water)
- for research purposes (marine science, polar research)
(see also Manual on Hydrography of the International Hydrographic Organization (IHO) under web links).
About 80% of the transports in the world economy are carried out by sea. The shipping routes must be monitored regularly to avoid accidents. There are still inadequately mapped areas whose driving represents a danger to nature (including people). Driving into areas with not updated nautical charts is not permitted.
Tasks of hydrography in Austria (using the example of the hydrographic service in Carinthia)
The area of responsibility of hydrography in Carinthia includes the comprehensive survey of the water cycle by observing and recording the amount of precipitation, air and water temperature, evaporation, ground, flowing water and lake water levels as well as inflows and outflows. These observations and measurements enable the recording of water resources, show changes in the water balance and subsequently serve to solve a wide variety of water management tasks and problems.
Core tasks of the Hydrographic Service in Carinthia:
- Measurement network construction, maintenance and optimization
- Measurement service and data acquisition (analog and digital recordings)
- Data transmission (long-distance transmission network), processing and evaluation
- Data management and hydrological data service
- Hydrographic / hydrological evaluations, analyzes and studies
- Hydrographic review of hydraulic engineering and water management projects
- Flood warning service (disaster)
- Expert activity in the administrative procedure
- Hydrological reports
education and profession
Hydrographs are wanted, the possible uses are diverse. The fields of activity range from the programmer in the office to the measuring user on the ship. There are good opportunities to work abroad.
Access to the profession is gained through studying geomatics or related areas, including geosciences. In German-speaking countries, there is a special English-language version of the 2-year M.Sc. Geomatics at the HafenCity University Hamburg (HCU) with the highest international certification (FIG / IHO / ICA Category A). Admission requirements: Bachelor or diploma in a related subject, proven knowledge of English. Good knowledge of mathematics, physics and geography and a good technical understanding are helpful.
Apprenticeship: marine surveying technician in public administration
Further training opportunities, for example, through DHyG, DVW, TECHAWI, Kiel University, and HCU.
Measurement methods
Hydrographic measurements under water are dominated by acoustic methods ( echo sounders , sonars ) in connection with satellite-supported positioning of the measuring location. Exemplary measurement methods are
- Positioning of the ship to the centimeter via GNSS (GPS, GLONASS ...)
- Determination of the position angle (course, roll, pitch) of the ship via GNSS or inertial sensors
- Depth measurements with single beam and multibeam echosounders
- Determination of sediment thicknesses with sediment echo sounders
- Pictorial representation of morphology and objects with SideScan sonars
- Detection of magnetic metal parts (wrecks, anchors) with magnetometers
- Determination of flow velocities and directions with ultrasonic Doppler profile flow meters (ADCP)
With modern measuring methods several thousand points per second can be measured. Some sensors can also be used to make statements about the nature of the seabed.
Historically, depth measurements were initially carried out using purely mechanical sounding using a rod or plumb bob on a line or wire; later also by means of a compressed air solder with a drawn hose and other methods that measure the water pressure.
More about the measurement methods can be looked up in the IHO's freely available Manual on Hydrography (see web links).