(1) In well logging. In a horizontal plane, it is the clockwise angle of departure from magnetic north. See also [[magnetic declination]].

(2) [[Curve]] recorded in [[dipmeter]] surveys. Looking down the hole, it is the clockwise angle from magnetic north to the reference electrode number 1 on the [[sonde]] or tool.

(3) In land surveying. It is the clockwise angle of departure in a horizontal plane from true north.


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