fiducial axis

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 termed fiducial mark. See collimating marks.
An Illustrated Dictionary of Aviation Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved
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