However, because it’s so difficult to get a precise estimate, there is a large margin of error for both the government figure and the Columbia number. The margin is so large that the two estimates essentially overlap, the researchers said. Their study was published online yesterday in the journal Science.
The director of the US Geological Survey, Marcia McNutt, who oversaw federal estimates of the spill size, called the Columbia study “a completely independent and unbiased verification of the government result.’’
Tim Crone of Columbia, the lead researcher who calculated his estimate based on detailed flow formulas determined by watching video of the leak, said: “Our numbers overlap, so sure, we agree.’’
But Crone said he is more confident in his estimate because it went through the rigorous independent peer review required to be published in a respected journal. He added that it is hard to compare in depth with federal numbers “because few details of their methods have been released.’’
Crone used a different technique to study video than most scientists who analyze flow rates from video. Usually, scientists track particles and calculate a speed as they travel across a screen, much like watching a car race down a highway.
But in this case the particles were hard to track, so Crone used a technique he has been working on for a decade. He studies individual points in the video — all the points — and watches their changes in color and texture. For this study, Crone reviewed video from two dates, May 15 and June 3, and extrapolated for the spill estimate.
