Where Are the Live Bombs? Computer vision identifies unexploded bombs in Cambodia.

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2 min read
Map seen with computer vision

Unexploded munitions from past wars continue to kill and maim thousands of people every year. Computer vision is helping researchers figure out where these dormant weapons are likely to be.

What’s new: Data scientists at Ohio State University combined computer vision with military records to identify areas in Cambodia where bombs dropped by U.S. planes during its war on neighboring Vietnam remain unexploded.

How it works: The U.S. Air Force kept records of how many bombs it dropped in each air raid, but no one knows how many failed to detonate. The researchers built a tool that counts craters — evidence of bombs that did explode — and then subtracted that number from the total number dropped. The difference enabled them to estimate how many bombs still litter the countryside.

  • The researchers hand-labeled 49 craters in satellite imagery, along with 108 other circular objects (such as trees and rice silos) within a 1.5 square kilometer training area. By flipping and rotating the crater images, they increased the training dataset to 1,256 total labeled images.
  • The craters can be hard to spot, blurred by decades of erosion and overgrowth and often filled with water. So the researchers developed a two-step model that first identifies potential craters and then culls false positives.
  • Step one picked out everything that was circular enough to look vaguely like a crater. It identified 1,229 candidates in the validation area of 9.2 square kilometers (the image with more blue dots in the animation above).
  • In step two, the model compared the candidates’ color, shape, size, and texture with craters in the labeled data. Using a decision tree, it correctly identified 152 of 177 verified craters in the area (the image with fewer blue dots).

The results: The researchers used their model to sweep a 100 square kilometer area near the Vietnamese border that had been slammed with 3,205 bombs during the war. Using multiple runs of their model, the researchers found between 1,405 to 1,618 craters, which suggests that up to half of all the bombs dropped in this area are still waiting to be found.

Behind the news: In 1969, U.S. President Richard Nixon secretly ordered the Air Force to begin bombing Cambodia to disrupt Viet Cong supply lines. The campaign left between 50,000 and 150,000 dead. Since then, unexploded bombs and landmines have killed or maimed at least 60,000 people in Cambodia.

Why it matters: Bombs from past wars pose a present danger to people all over the world. But finding them is expensive and labor-intensive. Models that map high concentrations of unexploded ordnance could help organizations working on the problem direct their resources more efficiently.

We’re thinking: It’s heartening to see the technology of the future applied to problems created in the past.


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