By JEFFREY R. YOUNG
Equipped with lasers or customized Palm Pilots, teams of
university researchershave been assessing the damage done to
the buildings surrounding the World Trade Center during the
September 11 terrorist attacks.
The groups, many of them supported by the National Science
Foundation, are using new high-tech methods developed for
surveying earthquake and hurricane damage -- but in this case
the researchers are making sure that the buildings surrounding
the fallen trade towers are safe to reoccupy. Some of the
assessment techniques have never been used in the field.
One of the researchers who raced to study the incident was
David Bloomquist, an associate professor of civil and coastal
engineering at the University of Florida. Officials from the
Defense Department asked Mr. Bloomquist and other Florida
researchers to use an airborne laser to map the damage done to
The laser-measuring device is capable of determining the
topography of an area to within a one-centimeter margin of
error. That is far more detailed than traditional methods,
which rely on aerial photography. The team will remap the area
in the coming weeks to look for shifts in the structures.
The team also plans to use a ground-based laser system to map
portions of Ground Zero, and to combine that information with
the aerial data to increase the resolution of their maps even
further. When combined, the data will be used to make
"three-dimensional models of the disaster sites far more
detailed and accurate than has ever before been available to
recovery workers and planners," according to a grant proposal
submitted to the NSF by the researchers.
Unfortunately, the university's airborne laser was in the shop
for an upgrade at the time of the attacks, so the team raced
to borrow another laser system, with the help of the National
Oceanic and Atmospheric Administration. Twelve days after the
attacks, some of the researchers were on their way to New
Crisscrossing the sky
Michael Sartori, a research coordinator for the group, and a
graduate student, Devon Drake, drove a sport-utility vehicle
from Gainesville to Ground Zero because they did not want to
fly. "Every overpass had an American flag on it," says Mr.
"I was glad to go and be part of it," he adds. "We felt like
we were able actually to do something."
Mr. Sartori was on ground duty while the plane equipped with
the laser system crisscrossed the sky above Manhattan at 3,800
feet -- high enough so that it would not worry residents who
might fear another attack. He stood in a field near a New
Jersey airport using a global-positioning system that tracked
the airplane's progress. That night, Mr. Sartori began
analyzing the data in his hotel room, using a desktop computer
he brought with him.
"We've got over 100 million data points collected," says Mr.
Bloomquist. From the data, the team has already generated
haunting three-dimensional computer images of the area.
Because the software they use was designed to assess
geological features, the buildings and streets around Ground
Zero look like a series of cliffs and valleys, with a crater
where the trade towers once stood. Some of the images are
available on the university's Web site
In the next few weeks, the team plans to make another flyover
and to compare the two sets of data. The university's own
airborne laser system will be back in operation by then, and
Mr. Bloomquist, who is a licensed pilot, intends to fly a
twin-engine Cessna with the laser over the trade towers'
"With the laser you can say a building has shifted a
centimeter on this end," says Mr. Bloomquist. "From the naked
eye you couldn't tell."
As the researchers spell out in their grant proposal, some
buildings may be faltering. "Several surrounding buildings
near Ground Zero may not be structurally salvable, and there
is concern that several are slowly deteriorating from a
structural standpoint," they wrote.
Meanwhile, a team of scholars from the Georgia Institute of
Technology traveled to Ground Zero with Palm Pilots equipped
with customized software to help them record the damage done
to surviving buildings. They arrived just two weeks after the
attacks, in part because they wanted to document the damage
before anything changed.
James David Frost, an engineering professor at Georgia Tech,
originally developed the Palm Pilot software, which he calls
PQuake, to log building damage done by earthquakes
software features a series of menus that make it easy to
record the structural characteristics of buildings while the
researcher is looking at them. Using GPS, the software can
match the researcher's exact location with the data gathered
during each observation.
Mr. Frost says a key benefit of the software is that it makes
it easy to keep notes and pictures organized, and to share
them with colleagues. "It means I can just send you my files
electronically, and I don't have to be sitting beside you
saying this is the photo that goes here."
As horrible as the destruction was, Mr. Frost says that there
was less damage than he expected to some structures near the
fallen trade towers.
In many cases, he says, "the integrity of the building is
probably not compromised." But he added that due to cosmetic
damage done to the buildings, it could be "six to nine months"
before buildings with even minimal damage can be reoccupied.
Researchers from various groups who are assessing damage at
Ground Zero are also working to create a joint database to
share information. New York University is organizing a
workshop on December 12-13 for the various teams to meet and
share their findings.