Overlays - Aerial Photograph Overlay
73. AERIAL PHOTOGRAPH OVERLAY
Overlays of single aerial photographs are constructed and used in the same way as map overlays. The steps followed are essentially the same, with the following exceptions:
a. Orienting of Overlay. The photograph normally does not have grid lines to be used as register marks. The borders of the photograph limit the area of the overlay, so the reference marks or linear features are traced in place of grid register marks. Finally, to ensure proper location of the overlay with respect to the photograph, indicate on the overlay the position of the marginal data on the photograph as seen through the overlay.
b. Marginal Information. The marginal information shown on photographs varies somewhat from that shown on maps. Overlays of photographs should show the following information:
(1) North arrow. This may be obtained in two ways--by comparing with a map of the area or by orienting the photograph by inspection. In the latter case, a compass or expedient direction finder must be used to place the direction arrow on the overlay. Use the standard symbol to represent the actual north arrow used--grid, magnetic, or true north.
(2) Title and objective. This tells the reader why the photo overlay was made and may also give the actual location.
(3) Time and date. The exact time the information was obtained is shown on a photo overlay just as on a map overlay.
(4) Photo reference. The photo number, mission number, date of flight, and scale appear here, or the information is traced in its actual location on the photograph.
(5) Scale. The scale must be computed since it is not part of the marginal data.
(6) Map reference. Reference is made to the sheet name, sheet number, series number, and scale of a map of the area, if one is available.
(7) Author. The name, rank, and organization of the author are shown, supplemented with a date and time of preparation of the overlay.
(8) Legend. As with map overlays, this is only necessary when nonstandard symbols are used.
(9) Security classification. This must correspond to the highest classification of either the photograph or the information placed on the overlay. If the information and photograph are unclassified, this will be so stated. The locations of the classification notes, and the notes will appear in both locations.
(10) Additional information. Any other information that amplifies the overlay will also be included. Make it as brief as possible.