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A base elevation used as a reference from which to reckon heights or depths. It is called TIDAL DATUM when defined by a certain phase of the tide. Tidal datums are local datums and should not be extended into areas which have differing topographic features without substantiating measurements. In order that they may be recovered when needed, such datums are referenced to fixed points known as bench marks. See also CHART SOUNDING DATUM.
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Related Terms |
PEN RECORDER
A device in which the varying inputs (electrical, pneumatic, mechanical) are marked by a signal-controlled pen onto a continuous recorder chart (circular or roll chart).
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OPERATOR PROCESS CHART
A chart of the time relationship of the movements made by the body members of a workman performing an operation.
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OPEN-TIMBERED ROOF
A roof in which the 381 operation process chart operations sequence entire process, including the points at which materials are introduced, the sequence of inspections, and all operations not involved in material handling.
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MULTIPLE CONNECTOR
A flow chart symbol that indicates the merging of several flow lines into one line or the dispersal of a flow line into several lines.
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MULTIPLE-ACTIVITY PROCESS CHART
A chart showing the coordinated synchronous or simultaneous activities of a work system comprising one or more machines or individuals; separate, parallel columns indicate each machine's or person's activities as related to the other parts of the work system.
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HUMAN-MACHINE CHART
A two-column, multiple-activity process chart listing the steps performed by an operator and the operations performed by a machine and showing the corresponding idle times for each. Also known as man-machine chart.
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HEIGHT OF TIDE
Vertical distance from the chart sounding datum to the water surface at any stage of the tide. It is positive if the water level is higher than the chart sounding datum. The vertical distance from the chart sounding datum to a high water datum is called RISE OF TIDE.
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INDEX CHART
An outline chart showing the limits and identifying desig- nations of navigational charts, volumes of sailing directions, etc.
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NATIONAL WATER LEVEL OBSERVATION NETWORK
A network composed of the primary control tide stations of the National Ocean Service. This network of coastal observation stations provides the basic tidal datums for coastal boundaries and chart datums of the United States. Tidal datums obtained at secondary control tide stations and tertiary tide stations are referenced to the Network.
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ENC
Electronic Navigational Chart
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