In the context of aerial photographs, what is made up of fiducial marks?

The principal point is a crucial element in aerial photography, representing the point in an image where the optical axis of the camera intersects the photograph. Fiducial marks are reference points that are placed on the film or digital sensor to assist in accurately determining the location of this principal point. These marks are essential for calibration and to ensure consistency in measurements taken from the photographs. By finding and using the fiducial marks, surveyors can rectify images, which means adjusting the photographs to accurately represent the ground features they depict. This correction helps eliminate distortions caused by the angle of the camera and the terrain.

Understanding how fiducial marks denote the principal point is fundamental for surveyors as it enhances the precision and reliability of spatial data derived from aerial imagery.