The University of Arkansas Center for Advanced Spatial Technologies (CAST) has been hard at work on an online repository of declassified Corona satellite images dating from 1968-1972 with grant funding from the National Endowment for the Humanities and the American Council of Learned Societies. The resulting CORONA Atlas of the Middle East is now online with 700 images that will eventually expand to host more than 1,500 images. This valuable historical link to the past provides both online viewing and the download of full-resolution images in GeoTiff or NITF formats.
Corona is the codename for the United States’ first photographic spy satellite mission that took high-resolution images over much of the planet, with an emphasis of collection in Soviet bloc countries. The imagery was declassified in 1995 and has been available through the U.S. Geological Survey. While the imagery has been valuable, it has also proven problematic given the long narrow film strips collected by the camera that introduce spatial distortions that are hard to correct and a lack of metadata that have made it hard to geolocate the images. Over the years researchers have developed models and methods to process the images, and recent advances in image processing have made online processing possible.
CAST puts the historical imagery through a rigorous set of photogrammetric workflows to mosaic images into panels, collect ground control points, triangulate blocks of images, and calibrate the sensor model. The technical aspects of this process are described in a forthcoming paper that will be published in the International Journal of Remote Sensing. They then use Esri’s ArcServer 10 for hosting and to orthorectify NITF images on-the-fly. Google Maps data is used for its high-resolution imagery, which enables ground control to be collected efficiently.
There are a number of tools available on the site that enhance viewing and imagery analysis. There is a slider to adjust the transparency of the Corona image, a search window to find a specific location, and a measurement tool for linear measurement. There are a number of resources available for help on downloading and working with the Corona images via the Help tab on the site. The final version of the Atlas will allow users to analyze and compare CORONA imagery with modern Google data.
Given rapid industrialization and development in the middle east over the past fifty years, this archive is of particular interest to archaeologists to understand the landscape and changes that have take place around archaeological sites. The site incorporates a detailed list of quick links to archaeological sites across the region. A quick jump to any number of these sites shows that the pace of change is quite striking.