Home > Public Domain Data > 50-60 year old Spy Imagery as a source of historic data

50-60 year old Spy Imagery as a source of historic data

Throughout the 1960s and 1970s a top-secret US program dubbed Corona by the Central Intelligence Agency (CIA) captured 800,000 images via satellite of many places around the planet. As an interesting piece of GIS and remote sensing history, the film canisters from these satellites was periodically jettisoned, and physically retrieved in midair via aircraft. The logistics involved in such operations are amazing for their time, and even now. The imagery was declassified in 1995. At that time, I was working as a cartographer for the USGS, and we started offering prints of the Corona imagery then. I remember poring over these prints at our large mapping facility in Denver, considering the vast amount of change evident in a relatively short (30 years) time since they had been collected.

New developments in GIS technology are breathing new life into this set of imagery, making it increasingly available and applied to a wider variety of uses. For example, my colleague Mariah Petrovic wrote a fascinating article about how this imagery is being used to address climate change, here. These include past habitats, water scarcity, and shoreline change. In addition, the imagery is being used to identify archaeological sites and much more.

Now some of this imagery is available in digital form as part of the growing array of truly Big Data sets. One way to access is via the USGS Earth Explorer portal. Another is via the Corona Atlas and Referencing System at the University of Arkansas. Some of the data accessible via the university’s data portal is from satellites that were equipped with two panoramic cameras, one facing forward and another aft, with a 30º angle of separation, producing an approximate ground resolution of 6 feet (1.8m) at nadir. They also offer the capability for stereo viewing, and the extraction of topographic data. Images were originally recorded on black-and-white film. The USGS scanned the images at 7 micron (3600 dpi) resolution. Additional technical details regarding the CORONA program and image characteristics can be read here.

Begin by exploring the data, available here. The atlas allows you to measure, identify, search, swipe, and perform other visualizations on the data. Map layers can be toggled using the Map Contents menu. Some map layers are expandable, allowing sub-layers to be turned on or off. Use the plus sign (+) next to a layer to access sub-layers. Use the blue down-arrow next to an image to download the source data, as shown below:

Downloading the Corona imagery.

The data formats include: (1) GeoTIFF – orthorectified and reprojected to use the “Web Mercator” projection. These should be ready for use in any GIS package that can read GeoTIFFs. The NITF version of this image will require the user to obtain appropriate elevation data to be used in the orthorectification process necessary to display the image in the correct position on the earth’s surface. More information about this process can be found here. This image has not been resampled as has the GeoTIFF listed above, so it is closer to the original imagery. The website helpfully provides coordinates that can be manually input as the data selection coordinates to download SRTM elevation data from OpenTopography.org; for example, for the image above: X-min: 32.428226 Y-min: 35.190579 X-max: 35.394672 Y-max: 35.827378.

Corona imagery for a section of Missouri USA.
Corona imagery for the Great Pyramids at Giza, Egypt.

I encourage you to investigate this amazing resource.

Joseph Kerski

Categories: Public Domain Data
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