 This application of the term evolved from air photo frame numbers that were originally used to locate geophysical survey lines in the early days of airborne geophysical surveying.This method of positioning has since been replaced by GPS, but the term "fiducial" continues to be used as the time reference for data measured during flights.In applications of augmented reality, fiducials help resolve several problems of integration between the real world view and the synthetic images that augment it.