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A chart datum is the water level surface serving as origin of depths displayed on a nautical chart and for reporting and predicting tide heights. A chart datum is generally derived from some tidal phase, in which case it is also known as a tidal datum. [1] Common chart datums are lowest astronomical tide (LAT) [1] and mean lower low water (MLLW).
The water level at each end of the tube will be at the same elevation, whether the two ends are adjacent or far apart, so a line between them will be horizontal at its midpoint and a shed base, building foundation or similar structure laid out using several such lines will be "horizontal" within building tolerances on any scale over which use ...
A variation of magnetic sensing is the "Hall effect" sensor which utilizes the magnetic sensing of a mechanical gauge's indications. In a typical application, a magnetism-sensitive "Hall effect sensor" is affixed to a mechanical tank gauge that has a magnetized indicator needle, so as to detect the indicating position of the gauge's needle.
Water gauge on a steam locomotive. Here the water is at the “top nut”, the maximum working level. Note the patterned backplate to help reading and toughened glass shroud. A sight glass or water gauge is a type of level sensor, a transparent tube through which the operator of a tank or boiler can observe the level of liquid contained within.
The first routine measurements of river flow in England began on the Thames and Lea in the 1880s, [2] and in Scotland on the River Garry in 1913. [3] The national gauging station network was established in its current form by the early 1970s and consists of approximately 1500 flow measurement stations supplemented by a variable number of temporary monitoring sites. [2]
In a well designed system, the existing water in the raceway is largely replaced by new water when the same volume of new water enters the raceway. Self-cleaning can sometimes be achieved if the fish stocks density is sufficiently high and the water level is sufficiently low. For example, if trout are stocked at 20 kilograms per cubic metre ...
A tide gauge The tide gauge in Kronstadt, Russia [1] A tide gauge is a device for measuring the change in sea level relative to a vertical datum. [2] [3] It is also known as a mareograph, [4] marigraph, [5] and sea-level recorder. [6] When applied to freshwater continental water bodies, the instrument may also be called a limnimeter. [7] [8]
3: Tube connecting the chamber to the low water side of the sluice 4: The chamber in which the water level can be controlled 5: Door with larger surface 6: Door with smaller surface. When the tube to the high water level side (1) is opened, the water level in the chamber (4) will rise to this same level.