Astigmatism Definition for Land Surveyors

astigmatism—An aberration affecting the sharpness of images caused by the fact that for objects off the axis the rays passing through different meridians of the lens come to a focus in different planes.   Thus, an extra-axial point object is imaged as two mutually perpendicular short lines located at different distances from the lens.   See also aberration of light (definition 2)

Source: NSPS “Definitions of Surveying and Related Terms“, used with permission.

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