Digital Terrain Models. Files are TIFF for the bitmaps and several options exist for line data. For processing transparencies of the aerial photos must be used, these are called diapositives. The scan of each diapositives occupies 180MB of computer disk space. Diapositives are clearer than prints.
Prints are relatively inexpensive and handy to help choose which diapositives to order.
Most of Australia has been photographed by National Mapping at scale of 1 in 80,000 using a super-wide lens. The scale of the diapositive is the quotient of the flying height divided by the camera lens focal length. The number of photographs required depends upon the height and flight path of the camera aircraft. Digital data on CD is optional. The number of models required to map a property will depend on its placement within the existing photography.