A systematic error in the observation of a quantity due to the personal idiosyncrasies of the observer. Also called PERSONAL EQUATION.
Related Terms |
HORIZON PRISM
A prism which can be inserted in the optical path of an instrument, such as a bubble sextant, to permit observation of the visible horizon.
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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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INVERTED COMPASS
A marine magnetic compass designed and installed for observation from below the compass card. Frequently used as a telltale compass. Also called HANGING COMPASS, OVERHEAD COMPASS.
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LAGRANGIAN CURRENT MEASUREMENT
The direct observation of the current speed or direction, or both, by a recording device such as a parachute drogue which follows the movement of a water mass through the ocean.
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LINE OF POSITION
A plotted line on which a vessel is located, determined by observation or measurement. Also called POSITION LINE.
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ALIDADE
The part of an optical measuring instrument comprising the optical system, indicator, vernier, etc. In modern practice the term is used principally in connection with a bearing circle fitted with a telescope to facilitate observation of bearings. Also called TELE- SCOPIC ALIDADE.
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ASSUMED LATITUDE
The latitude at which an observer is assumed to be located for an observation or computation, as the latitude of an assumed position or the latitude used for determining the longitude of time sight. Also called CHOSEN LATITUDE.
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ASTRONOMICAL POSITION
A point on the earth whose coordinates have been determined as a result of observation of celestial bodies. The expression is usually used in connection with positions on land determined with great accuracy for survey purposes.
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ASSUMED LONGITUDE
The longitude at which an observer is assumed to be located for an observation or computation, as the longitude of an assumed position or the longitude used for determining the latitude by meridian altitude. Also called CHOSEN LONGITUDE.
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NATIONAL TIDAL DATUM CONTROL 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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