Roughly, whether the water of interest is above mean sea level. Study of the Dead Sea and similar lakes also comes under the rubric "hydrography".
'Hydrography' is sometimes used synonymously with 'hydrology', but hydrography for the seas refers to the gathering of data to aid safe navigation, and as a development from that, wider uses to support exploration and development or environmental management.
Whereas oceanography may be seen as a science for the better understanding of the natural world, hydrography can be regarded as applied science supporting economic development and protection of Natural Resources.
There are areas of overlap: tidal studies, water quality, working from boats and ships. There are areas special to hydrography, such as geodesy (the shape of the Earth), datums (reference surfaces, both horizontal and vertical), applications to an individual country's mapping systems, measurement science (such as the technologies and deployment of survey instruments), boundary demarcation, and others.
Stig H. Fonselius has written: 'Hydrography of the Baltic deep basins' -- subject(s): Oceanography, Salinity 'On the stagnant conditions in the Baltic' -- subject(s): Chemical oceanography
Echosounders are primarily used for measuring the depth of water. They use sound waves to determine the distance between the sensor and the seabed or any underwater object. This technology is commonly used in navigation, fishing, hydrography, and oceanography.
Wayne V. Burt has written: 'Use of on-line computers in environmental research' -- subject(s): Research, Environmental monitoring, Meteorology, Oceanography, Environmental sciences, Oceanographic buoys, Computers 'Water temperature studies on the Snake River' -- subject(s): Temperature, Water temperature, Rivers 'Hydrography of Oregon estuaries' -- subject(s): Estuaries, Estuarine oceanography, Hydrography, Tables
Correction: What is hydrographic datum? not "hydrography"
Charles Fitzpatrick has written: 'Temperature, salinity and density atlas for Station 27' -- subject(s): Observations, Ocean temperature, Oceanography, Hydrography, Oceanographic research stations, Salinity
Johannes Schmidt has written: 'Danish eel investigations during 25 years, 1905-1930' -- subject(s): Eels 'Introduction to the oceanographical reports' -- subject(s): Dana (Ship), Hydrography, Oceanography
Oceanography.
Oceanographers study the patterns and chemical properties in the ocean. Some types of oceanography include physical oceanography, geological oceanography, chemical oceanography, and biological oceanography.
geological oceanography biological oceanography
Oceanography, also called oceanology or marine science.
The prefix for Oceanography is "ocean-".
Alan P. Trujillo has written: 'Essentials of oceanography' -- subject(s): Oceanografi 'Essentials of oceanography' -- subject(s): Oceanography 'Essentials of oceanography' -- subject(s): Oceanography