Tuesday, February 17, 2009

Finding Osama bin Laden using remote sensing

While U.S. intelligence officials have spent more than seven years searching fruitlessly for Osama bin Laden, UCLA geographers say they have a good idea of where the terrorist leader was at the end of 2001 — and perhaps where he has been in the years since.

In a new study published online today by the MIT International Review, the geographers report that simple facts, publicly available satellite imagery and fundamental principles of geography place the mastermind behind the Sept. 11 attacks against the U.S. in one of three buildings in the northwest Pakistan town of Parachinar, in the Kurram tribal region near the border with Afghanistan.

Despite keen interest in the terrorist recluse and a $25 million reward for information leading to his capture, academics have shied away from getting involved in the quest to find him, the researchers contend. Meanwhile, dramatic improvements in remote-sensing imagery have improved the odds of civilians doing so.

The researchers advocate that the U.S. investigate — but not bomb — the three buildings. They warn that if bin Laden indeed remains to this day in the tiny city of Parachinar, or even elsewhere in the relatively thinly populated tribal area of Kurram, he may move to the city of Peshawar (population 1.4 million) in the neighboring tribal area of North-West Frontier Province if Peshawar falls to the Taliban. News reports have warned of that possibility since last summer.

The findings are based on the last information on bin Laden's whereabouts to be made public by U.S. intelligence sources, which have closely guarded the details of any efforts to locate him. One and a half months after the coordinated attacks on the World Trade Center and the Pentagon claimed the lives of more than 3,000 people, a walkie-talkie radio broadcast placed bin Laden in Tora Bora, a cave complex in eastern Afghanistan. In an unsuccessful attempt to capture bin Laden, U.S. forces attacked the caves the following month.

The UCLA findings rely on two principles used in geography to predict the distribution of wildlife, primarily for the purposes of designing approaches to conservation. The first, known as distance-decay theory, holds that as one travels farther away from a precise location with a specific composition of species — or, in this case, a specific composition of cultural and physical factors —the probability of finding spots with that same specific composition decreases exponentially. The second, island biogeographic theory, holds that large and close islands have larger immigration rates and will support more species than smaller, more isolated islands.

Inspired by distance-decay theory, the seven-member team started by drawing concentric circles around Tora Bora on a satellite map of the area at a distance of 10 kilometers — or 6.1 miles — apart.

Then, informed by island biogeographic theory, the researchers scoured the rings for "city islands" — or distinctly separate settlements of considerable size.

The approach netted 26 cities within a 12.4-mile radius of Tora Bora on imagery from Landsat Enhanced Thematic Mapper Plus (ETM+), a global archive of satellite photos managed by NASA and the U.S. Geological Survey. With a 2.7-square-mile footprint, Parachinar turned out to be the largest and fourth-least isolated city, the team determined.

The researchers ruled out cities on the Afghanistan side of the border because the country was occupied at the time by U.S. and international forces and has been particularly unstable ever since.

Faced with the prospect of picking from more than 1,000 structures clearly portrayed in the satellite imagery of Parachinar, the team decided to come up with a short list of the criteria that bin Laden would need for housing, based on well-known information about him, including his height (between 6'4" and 6'6", depending on the source), his medical condition (apparently in need of regular dialysis and, therefore, electricity to run the machine) and several basic assumptions, such as a need for security, protection, privacy and overhead cover to shield him from being spotted by planes, helicopters and satellites.

So they looked for buildings that could house someone taller than 6'4" and were surrounded by walls more than 9 feet tall (both as judged by mid-afternoon shadows depicted on the satellite imagery), and that had more than three rooms, space separating them from nearby structures, electricity and a thick tree canopy.

Only three structures fit the criteria. The buildings also appeared to be the best fortified and among the largest in Parachinar. Two are clearly residences, the study states. The third may be a prison. But whatever the third structure is, it has "one of the best maintained gardens in all of Parachinar," the study says.

While the three structures meet all six of the criteria that the researchers believe would be required for lodging bin Laden, an additional 16 structures in Parachinar appear to meet five of the six criteria. If bin Laden is not in the first three structures, the U.S. military should investigate these other buildings, the study urges.

The outgrowth of an undergraduate geography course in remote sensing, the study lists five 2008 UCLA graduates as co-authors. The students have since gone on to a range of endeavors, from selling real estate and attending law school to earning a master's degree from Oxford University. One now works for a remote-sensing company.

Undergraduates had attempted to take on the same study in 2006, but at 30 x 30 meters — or nearly 100 x 100 feet — the resolution of publicly available satellite images of the area at the time was insufficient. In contrast, today's resolution is 0.6 meters, or just under 2 feet, Gillespie said. The remote-sensing company that employs one of the alumni authors plans soon to unveil a 0.4-meter resolution of the entire world.

"Finding Osama bin Laden: An Application of Biogeographic Theories and Satellite Imagery" is not the first attempt by Gillespie and Agnew to bring scientific analysis to nettlesome political issues. In September 2008, they received widespread attention for a satellite study of the density of lights in the night sky of Baghdad in the time leading up to, during and immediately following the U.S. military surge of 2007. The findings cast doubt on the role claimed by the U.S. military in quelling violence during that time and suggest instead that intra-sectarian conflict was responsible for clearing whole portions of the city, leaving them both dark and devoid of the objects of Iraqi-on-Iraqi violence.

Source: http://web.mit.edu/mitir/


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