Researching Foreign Aerial Photography

Chances are that if you stop by the Cartographic Research Room on any given day, at least one person will be working with aerial photography.  It’s easily the most commonly requested record type in our research room and one of the most common offsite reference requests that we receive. The Cartographic Branch holds over 29 million aerial images. This includes photographic prints, rolled aerial negatives, and satellite imagery covering large areas of the United States and also many foreign areas.

This post focuses on how to locate, view, and copy foreign aerial photography, specifically rolled foreign aerial photography. This is the first post in a series that will include additional posts on both foreign and domestic aerial photography.

Getting Started

The majority of our foreign aerial photography is held within Record Group (RG) 373, Records of the Defense Intelligence Agency.  RG 373 also contains some coverage for areas of the United States. The first step in finding RG 373 aerial photography is to locate a specific geographic coordinate. The geographic coordinate, or latitude and longitude, may be found by using various online resources, such as Google Maps or the USGS’s EarthExplorer.

The next step is to view the Overlay Indexes for Aerial Photography of the Defense Intelligence Agency, which are available online through the National Archives Catalog or may be viewed on microfilm in our research room. These indexes are arranged by the coordinates of the degree square. The easiest way to search these indexes on the National Archives Catalog is enter the degree square into the catalog using the following format: 33N130E or 49N008E. The latitude must be two digits in length and followed by either N or S for north or south. The longitude must be three digits (use leading zeros if necessary) and is followed by either a W or E for west or east.

For example, if we are looking for aerial photography of Brussels, Belgium, we first locate the geographic coordinates, which are 50.849735, 4.361687. To search the catalog, we enter 50N004E into the search bar.

The following result should appear:

Catalog Search - Brussels
Searching for Aerial Overlays on the National Archives Catalog. Overlays are searched by geographic coordinate (example 50N004E for Brussels, Belgium).

Click on the blue hyperlink to view the record, which will display the following:

Load More Example - Brussels
Example of Overlay as seen on the National Archives Catalog. The first image that is typically displayed is a cover sheet, listing the geographic coordinate. Note “load all” button near the bottom, which is circled.

The thumbnails are each a separate overlay. Each image represents what was originally a clear plastic sheet overprinted with boxes  and lines representing photographic exposures. These clear sheets were intended to be overlaid on top of a specific map to determine the geographic area each photographic exposure covered.

Typically, the overlays for a single degree square will contain a cover sheet (displayed in the example above) which lists the degree square represented by the overlays. The second image is typically an explanation of how to read each overlay sheet. The third image is typically a map that can be used with the overlays. (Note that occasionally no map is provided with the overlays, which makes them very difficult to use with any accuracy. If no map is provided, you will need to locate an appropriately scaled map to use instead, which is often very difficult to do.)

Locate your location on the map included with the overlay sheets. We suggest marking the location on the screen of your computer using a sticky note or other marker. In order to have the overlays line up with your marker correctly, you must mark your location while the map is fully zoomed out and reset to its original location. Otherwise, the overlays will not line up with the map. It also important not to scroll up or down on the screen once your location is marked.

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Example of placing the marker on the overlay, using the map near the beginning of the images. We recommend using a sticky note or other marker that can be affixed to the screen of your computer. Our marker is yellow, with the corner pointing at Brussels, our location of interest. Also note the reset button, which is circled and labeled. If the image is not reset before placing the marker, the overlays will not line up correctly.

Once your location is marked, use the gray arrow to the right of the map to move through all of the images. If your marker lines up with any of the boxes, which represent photographic exposures, it means that imagery exists for that location.

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Example showing the yellow marker lined up with the boxes indicating photographic exposures. This means that coverage exists for our location. The information needed to locate the photographs can be found on this overlay index sheet.

The next step in the process is to examine the top of the overlay index sheet and see if it contains a spot number (described below) or a GX or TUGX number (will be featured in a feature post focusing on Captured German Aerial Photographic Prints).

Overlays with Spot Number References

Overlays that contain a spot number near the top lead to rolled aerial photographic negatives within RG 373, Aerial Photographs.

Spot numbers can be found near the top of the index and typically include a letter followed by a number, although they can just include a number. Sometimes, a single overlay may list multiple spot numbers if the negatives are found on multiple rolls of film. Spot numbers are typically handwritten on the overlays rather than typed.

If no spot number is listed on an overlay, it means that unfortunately the National Archives is unable to link that overlay to a specific can of rolled aerial negatives within our holdings.

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Example showing the spot number (E403) and the Exposure Number (41). The triangle’s bottom point is the marker for our location, which falls between exposures 41 and 46. The line between the box labeled 41 and the box labeled 46 indicates consecutive photographic exposures.

Another important thing to note on the index sheets are the exposure numbers that line up with the area of interest marked on your screen (remember to reset the overlay to ensure the map and overlay sheet are lined up correctly). The boxes shown on the overlay correspond to individual photographic exposures. In the case of the overlay used in the example, the point of the marker for Brussels falls between the box marked 41 and the box marked 46. The line between the boxes is used to indicate continuous exposures, so exposures 41 through 46 are represented by the two boxes and the line that connects them. There is considerable overlap of the exposures, so the area of interest may appear on multiple exposures. In this case, we can estimate that the center of Brussels is covered by approximately exposure 45, although the surrounding exposure numbers may also cover this area.

It can also be helpful to pay attention to the date, scale, and photography quality noted on the overlay. If the quality is listed as poor, or clouds are indicated, the view of the ground may be obscured in the photograph.

After noting the spot number and exposure numbers, the next step is to check the spot number against the RG 373 Can Locator to determine which can of rolled aerial negatives contains the imagery. The can locator is available in paper and electronic formats in the Cartographic Research Room. It is not available online.

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Example of our Can Locator, which can be viewed electronically or in paper during a visit to our research room. The Can Locator allows us to match up a spot number with a specific can of rolled aerial negatives.

Please note the can number and the barcode (if there is one). DN cans (duplicate negatives) are stored on-site and may be requested as a same day pull at our College Park, Maryland research room. These do not have a barcode. ON cans (original negatives) are stored off-site at a facility in Lenexa, Kansas for preservation reasons and must be ordered in advance to view in our College Park, Maryland research room. Note that these must be viewed in College Park and cannot be viewed in Lenexa. There is an approximately 3 business day wait to view the film in College Park after it has been ordered. Orders for up to 10 cans per day may be placed in person, or in limited circumstances, may be requested by emailing us at carto@nara.gov. The order form is available in our research room or may be downloaded here: Cold Storage Request Form. 

Viewing and Copying Rolled Aerial Negatives

Aerial photography that is located using a spot number is formatted as rolled aerial negatives, typically each approximately 9 inches by 9 inches. Rolled aerial negatives may be viewed, photographed, and/or scanned in the Cartographic Research Room. Light tables are available to view the rolled aerial negatives. Researchers may take non-flash photos using their own personal camera or smartphone. Tripods are also permitted.

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Light tables are available to view the rolled aerial negatives.
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Rolled Aerial Negatives as viewed on a light table in the Cartographic Research Room.

Additionally, two special scanner boxes are available in the Cartographic Research Room to scan rolled aerial negatives. One scanner is an Epson Expression 11000XL Photo Scanner and one is a Microtek Scanmaker 9800XL plus. Researchers must supply their own laptop computers, which will need to be connected to the scanner by USB. Free software for the scanners will also need to be downloaded to the personal laptop before completing scans. The scanners are compatible with both PCs and Macs. Please note that making high resolution scans of rolled aerial negatives is very time consuming and can take up to 10 minutes or more per scan depending on the resolution. Also note that the scanners are subject to availability and time on the scanner may be limited if other researchers are waiting to use them. Sign up sheets are available in the consultation office in our research room.

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Epson Scanner with aerial film box for scanning rolled aerial negatives. There is no charge to use either of our aerial scanners, although you must sign up before using them. 
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Microtek scanner for scanning rolled aerial negatives. This scanner is easier to use than the Epson, so is recommended for first time users. 

This post is the first in a series that will provide information about how to research and locate aerial photography. In future posts, we will highlight how to locate and access Captured German GX Prints (RG 373) and aerial photography covering the United States (RG 145 and RG 114).

Researchers are always also welcome to visit the Cartographic Research Room at Archives II in College Park, Maryland for more information on accessing our aerial photography holdings.

 

 

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