Focusing on the responsible application of geographic technologies across a range of human rights and humanitarian issues and how these technologies can be used to improve research and documentation.
The Use of Declassified US Government Satellite Imagery for the Investigation of Possible Gravesites in Argentina
In October 2009 the Geospatial Technologies and Human Rights Project of the American Association for the Advancement of Science (AAAS) undertook a review of satellite imagery acquired of three areas in Argentina: San Miguel de Tucumán, Santa Fe, and Loma del Torito. The analysis was conducted at the request of the Argentine Forensic Anthropology Team (EAAF), based in Buenos Aires, which works to identify the remains of victims from gravesites created during Argentina’s Dirty War, which lasted from 1976-1983. At least 9,000 political dissidents and other individuals were kidnapped, with many executed and buried at secret facilities during this period. AAAS was tasked with surveying satellite imagery of areas where graves were thought to have been created between 1976 and 1978. Using declassified US Government satellite imagery from the KH-9 satellite series, AAAS identified changes to the land in each of the three areas, though the quality of the imagery did not allow for identification of the reported gravesites.
AAAS obtained declassified US Government satellite imagery from the 1970s and recent high-resolution imagery to analyze the three areas of interest for possible changes that may indicate the presence of graves. Based on information about the likely timeframe during which the graves were created, AAAS obtained “before” and “after” images from the archives of the KH-9 satellite series. These images were among thousands of others taken between 1963 and 1980 that were declassified by the US Government in 2002 by Executive Order 12951. Using USGS’s Earth Explorer site, KH-9 images for each of the three areas were found and ordered. While the USGS claims a 7-9 meter imaging resolution for the KH-9 satellites, the panchromatic images AAAS received had a finer 5 meter resolution. The KH-9 images were not georeferenced upon receipt, so some effort was required to rectify them.
In addition to the declassified imagery, recent high-resolution images were obtained from DigitalGlobe’s QuickBird satellite to determine the extent of change between the events of the 1970s and now. For the Loma del Torito area, a 2009 GeoEye image available on Google Earth was sufficient to conduct the analysis. A list of all the images used in this analysis can be seen in Table 1 below.
Table One: Imagery Information
|Area of Interest||Image Date||Sensor||Resolution|
|San Miguel de Tucuman||10/01/2007||QuickBird||61 cm pan, 2.4 m multi|
|05/22/1978||KH-9||~ 5 m|
|09/04/1977||KH-9||~ 5 m|
|Santa Fe||01/27/2006||QuickBird||61 cm pan, 2.4 m multi|
|09/05/2002||QuickBird||61 cm pan, 2.4 m multi|
|04/23/1978||KH-9||~ 5 m|
|08/06/1973||KH-9||~ 5 m|
|Loma del Torito||08/21/2009||GeoEye-1 (from Google Earth)||0.41 cm pan, 1.65 m multi|
|05/31/1978||KH-9||~ 5 m|
|07/19/1976||KH-9||~ 5 m|
Analysis of the three areas in Argentina was conducted based on declassified satellite imagery from the 1970s and more recent high-resolution imagery from this past decade. For each area, AAAS visually compared the 1970s “before” and “after” images, and then compared the 1970s “after” image to the recent high-resolution image, noting any changes that occurred.
The San Miguel de Tucumán analysis looked at images from September 4, 1977; May 22, 1978; and October 1, 2007. The area of interest is a heavily forested area that, based on testimony, used to house an illegal detention center. The area is thought to contain a mass grave holding roughly 200 bodies. The most significant changes that occurred were in the roads within the forested area. In 1977, several small roads traverse the area, and by 1978 most, but not all, of these remain. However, in the 2007 image, very few roads are visible from above. The disappearance of the roads could signal the overgrowth of vegetation in areas that were once accessible. Additionally, a few forested areas from the 1970s appear to have been deforested altogether by the 2007 image, with development or cropland replacing them.
Figure One: San Miguel de Tucumán
1977: In this first image, several roads and a wheel-and-spoke network of paths (in the upper-right quadrant) are visible. Image USGS.
1978: The network of paths is no longer visible, but most other roads are. Image USGS.
2007: In this final image, many roads are now entirely obscured or overgrown by tree cover. Image DigitalGlobe.
Analysis of the Santa Fe area was conducted using three separate images taken August 6, 1973; April 23, 1978; and September 5, 2002. Based on witness accounts, a small number of bodies are thought to be contained within a 3 km by 7 km tract of land near Santa Fe. Most of the detected change was in the amount of tree canopy cover. Much of this change was likely due to seasonal variation. It is important to note that the 1973 image was of slightly worse quality than the 1978 image, and may have inhibited a more thorough analysis of the area.
Figure Two: Santa Fe
1973: In this early image, several darkened areas, possibly tree clusters, are apparent. Image USGS.
1978: A few of these areas, particularly in the upper-right quadrant of the image, have expanded. Image USGS.
2002: Decades later, patches of exposed soil dot the land, replacing what may have been clusters of trees in the earlier images. Image DigitalGlobe.
The Loma del Torito analysis utilized three images, taken on July 19, 1976; May 31, 1978; and August 21, 2009. The most significant change was found between 1976 and the latter images. In this early image, a small road appears to lead to an enclosed area that is possibly walled off. While the 1978 image shows no similar structures, the 2009 image reveals what appear to be two small buildings. The location of this change matches one of the areas of interest within the Loma del Torito area, and may warrant further investigation. In addition, a few roads that are visible in the 1976 image are not in the 1978 image.
Figure Three: Loma del Torito
1976: In this first image, a road leads to what appears to be a large, fenced-in area. Image USGS.
1976: The green outline delineates the possible complex. Image USGS.
2009: The area now has two small structures with no noticeable road. Image obtained via Google Earth.
While no conclusive evidence of gravesites was found in the three areas, significant changes in roads and structures provide an opportunity for further investigation. According to EAAF, the changes detected in the Loma del Torito area were sufficient for a judge to grant the group access to begin some preliminary forensic work on the land.