Steven Wereley, an associate professor of mechanical engineering at Purdue University, analyzed videotape of the seafloor gusher using a technique called particle image velocimetry.
A computer program simply tracks particles and calculates how fast they are moving. Wereley put the BP video of the gusher into his computer. He made a few simple calculations and came up with an astonishing value for the rate of the oil spill: 70,000 barrels a day -- much higher than the official estimate of 5,000 barrels a day. [...]"We're talking more than a factor-of-10 difference between what I calculate and the number that's being thrown around," he said. The size of the spill, as measured from satellites, seems to have grown about 50 percent from May 10 to late Thursday, said Graber from the University of Miami.
Moreover, the New York Times reported that scientists and environmental groups are critizing BP "for refusing to use well-known scientific techniques that would give a more precise figure" of the spill size.
The figure of 5,000 barrels a day was hastily produced by government scientists in Seattle. It appears to have been calculated using a method that is specifically not recommended for major oil spills.
Ian R. MacDonald, an oceanographer at Florida State University who is an expert in the analysis of oil slicks, said he had made his own rough calculations using satellite imagery. They suggested that the leak could "easily be four or five times" the government estimate, he said.
"The government has a responsibility to get good numbers," Dr. MacDonald said. "If it's beyond their technical capability, the whole world is ready to help them."
Scientists said that the size of the spill was directly related to the amount of damage it would do in the ocean and onshore, and that calculating it accurately was important for that reason.