- fiducial marks
- Any marker built into an aerial camera that registers its image on an aerial photograph as a fixed reference mark in the form of an image is called a fiducial mark. These are usually four fiducial marks on a photograph and are used to define the principal point of the photograph. Their appearance on the image permits various calibrations, such as determination of the degree of enlargement needed to fit the picture to the rectification grids. Fiducial marks are also marks in any instrument that define the axes whose intersection fixes the principal point of a photograph and fulfills the requirements of interior orientation. These are also usually four in number. See collimating marks.
Aviation dictionary. 2014.
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fiducial axis — The line joining opposite fiducial marks on a photograph. A fiducial mark is any marker built into an aerial camera that registers its image on an aerial photograph as a fixed reference mark. The image cast on a photograph by such a marker is… … Aviation dictionary
collimating marks — Index marks at the center point of each side of an air negative or photo. These are usually four in number, are rigidly connected with the camera lens through the camera body which forms images on the negative and usually define the principal… … Aviation dictionary
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