RESEARCH REPORTS

1. ARCHIVAL AERIAL PHOTOGRAPHY CONCERNED WITH ASIA AND THE PACIFIC AT THE U. S. NATIONAL ARCHIVES AND RECORDS ADMINISTRATION
by Leedom Lefferts

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Background: For the past several years the Cartography section of the U. S. National Archives and Records Administration (NARA), located at Archives II, College Park, Maryland, has been accessing aerial photography from around the world taken by the US Defense Intelligence Agency and its predecessors. Coverage dates from World War II untilthe development of excellent satellite photography. In addition, sometimes film from other, non-US agencies has also been acquired. This note provides general information for accessing this material that might be of interest to IPPA members and other researchers: The material becomes available as it is declassified by the US Department of Defense and the Defense Intelligence Agency. DIA is the US Government defense agency responsible for declassifying military photography and delivering the cans (rolls) of negatives or prints, as well as the indexes to this material, to NARA. This is very much a work in progress. Do not expect too much yet, but this may become an invaluable resource over the next 5 or more years.

Aerial Photographic Indexing: Archival aerial photography is indexed by "degree square", that is, by the degree of latitude and longitude of the site. The first step in discovering whether NARA has something in which you have an interest is to identify the geographic coordinates of that site, which, by definition, include the degree square by which aerial coverage will be discovered. Thus, Angkor/Siem Reap is within degree square 13 degrees north of the equator and 103 degrees east of Greenwich (13N x 103E). Sometime after each flight (sortie) during which photography was taken, an index of that flight was made. This "index" consists of a single sheet of transparent acetate, called an "overlay", or "trace". This overlay is scaled to fit over a map of 1:250,000 scale; these charts are referred to as WAC's (World Aeronautical Charts). The area the photo covers, or the strip of photos if the coverage was a strip, is indicated by a box or boxes on the overlay designating the area of the map covered by the photograph. Thus, the overlay has a box, or series of boxes, which fit over the actual area on the ground covered by the aerial photograph(s).

A single degree square may have several, maybe over a hundred, overlays. Each overlay provides an index for one flight. The researcher places the overlay on the base 1:250,000 map to discover whether that flight covered the site of interest.

Each overlay notes the following information: Organization & sortie (of the flight), Focal length of camera, Altitude (of aircraft), Scale (approximate), Exposures this degree square (the exposures taken on this flight which fall within this degree square), Total exposures (taken on this flight), Remarks, Date (Day, Month, Year), Time (Greenwich Mean Time), Country (covered), Snow cover, exposure numbers and % covered, Cloud Cover, exposure numbers and % covered, Op. File No., Overlay File No. (degree square coordinates for this overlay), Geo Ref (map number), Classification (security), Additional Security Information, Prepared by and date (name of person who indexed this flight on this degree square and the date of the indexing).

Details about the photography: Most photography was taken for military purposes; the military has been taking photography in Asia and the Pacific during and since the beginning of World War II. In addition, photography used for the (U. S.) Army Map Service World Wide Mapping Surveyof the late 1950's - early 1960's, which formed the basis of the detailed 1:50,000 scale charts of the early 1960's, is included. Scales vary, from the extremely detailed, e.g., 1:4,650, to mapping photography at 1:40,000+.

Much of the photography appears to be straight vertical, meaning that a camera was set in the belly of the aircraft pointing precisely downward. The camera was timed to take photos so that, usually, a certain percentage of overlap would occur between frames, usually 60%, as the plane flew along its flight path. Additionally, much of the photography would also have overlap between adjacent flight paths, approximately 40%. These overlaps sometimes provide stereoscopic coverage when viewed through the appropriate instruments. Additionally, some coverage is oblique, with the camera at an angle looking towards particular locations. The scale on oblique coverage, would, of course, not be the same for different areas of the photograph, but this coverage does provide a perspective view.

Often photography is not available but NARA has an overlay. In my experience, overlays are often available for which no film is currently present. I was told on this to keep checking back. Film is constantly being acquired.