Shape of things to comeAnalyzing shadows to catch terrorists
NASA scientist says that one way to catch terrorists is by marrying space-based surveillance with gait analysis biometrics: By analyzing the movements of human shadows in aerial and satellite footage it should be possible to identify people from the way they walk
Only the shadow knows: It is now seven years since Osama Bin Laden disappeared, and U.S. intelligence agencies are still chasing his shadow — and we use “shadow” here on purpose, since NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California says this is precisely what the intelligence community should be chasing. By analyzing the movements of human shadows in aerial and satellite footage, JPL engineer Adrian Stoica says it should be possible to identify people from the way they walk — a technique called gait analysis, the power of which lies in the fact that a person’s walking style is very hard to disguise.
Video taken from above shows only people’s heads and shoulders, which makes measuring the characteristic length and rhythm of a person’s stride impossible. This is not true of shadows, though, Stoica told a security conference in Edinburgh, Scotland, last month. Shadows, he says, provide enough gait data to deduce a positive ID. To prove it, he has written software that recognizes human movement in aerial and satellite video footage. It isolates moving shadows and uses data on the time of day and the camera angle to correct shadows if they are elongated or foreshortened. Regular gait analysis is then applied to identify people. In tests on footage shot from the sixth floor of a building, Stoica says his software was indeed able to extract useful gait data.
Extending the idea to satellites could prove trickier, though. Space imaging expert Bhupendra Jasani at King’s College London says geostationary satellites simply do not have the resolution to provide useful detail. “I find it hard to believe they could apply this technique from space,” he says.