By Darby Patterson
Government Technology Magazine
Incredible accuracy is a hallmark of the Digital Age. Measurements that were once unthinkable are readily available to anyone trained to use specialized equipment.
This sophisticated technology became a rescue and recovery tool in the immediate aftermath of the September 11 attack on New York City’s World Trade Center. After the collapse of the Twin Towers and the damage done to other buildings in the immediate vicinity, there was great concern about the safety of rescue workers digging through the rubble.
The rescue effort was hampered by billowing smoke, pockets of fire, and air thick with potentially dangerous chemicals. Heavy construction equipment had been called in to the site – cranes and earthmovers to pick up huge pieces of fallen steel and debris. The vibrations from the tons of vehicles promised to make the site even more unstable. There were constant concerns that more buildings would collapse and the remaining walls of the towers would come crashing down on emergency crews.
Throughout the 9-11 disaster, technology played a major role in New York City’s emergency management. Systems were installed on the periphery of Ground Zero to monitor any movement in the columns that stood like skeletons against the gray skies of New York. A unit was also used to watch the placement of a huge crane that would be used to move steel debris across a mass of rubble 400-feet wide.
The sensitive monitoring devices were provided by Topcon Positioning Systems located in Paramus, N.J., not too far from the scene of the disaster. The monitoring system, called GTS*, at first glance, looks a little like the viewing boxes at “vistas” along scenic highways. A metal box containing optical and electronic equipment sits atop a tripod. A laser beam is aimed at a distant target affixed to the structure to be monitored. Even the smallest shift of the beam from the target will be registered. An engineer can read the extent of movement in the building on a small computer screen. The equipment can read shifts as small as a quarter of an inch.
The crew established parameters for safety, and when those limits were exceeded, a loud horn alerted crews to evacuate the site. Topcon officials said the three-blast signal was sounded several times during the days following the disaster. Like other technology that came to the rescue after 9-11, the GTS system was not designed as an emergency tool. Instead, it is cutting edge surveying technology used by engineers in the building industry.
Geographic Information Systems (digital maps) were also used to monitor Ground Zero movement. These detailed pictures are created from data beamed to computers on earth from satellites in the sky. Global Positioning System (GPS) software inside the satellites track and send the data to back to earth. There are 27 satellites circulating the globe at an altitude of 12,600 miles and sending information to receiving stations all over the world.
Technologies such as GPS have become so sophisticated that they can compensate for the quirks of nature itself. Optical measurements and observations of elements on the ground are affected by atmospheric conditions that can diminish the accuracy of the equipment. Even though we think of space as a “void” there are many unseen impediments lurking there – including the atoms and molecules in the ionosphere.
This technology was first developed for military use, but its application in other arenas is almost unlimited. A Southern California company, Environmental System Research Institute, began using systems such as these to monitor changes in the global environment in the early 1980s. Most recently, their systems were used to assess the stability of fallen and damaged buildings in Manhattan. The idea that conditions on the ground can best be observed from the sky is not a new one, but its application as an emergency management tool was a welcome innovation for New York’s recovery team. ESRI has an extensive educational program that helps teachers make GIS technologies relevant in their classrooms.
Even in times of emergency, we are reminded that technology has made it possible to view the world in ways that even the great Galileo would not have imagined. We have moved beyond star gazing to open new windows to the planet on which we live.
*GTS is an acronym for the GNU Triangulated Surface Library. It is an Open Source Free Software Library intended to provide a set of useful functions to deal with 3D surfaces meshed with interconnected triangles. The source code is available free of charge under the Free Software LGPL license. This software allows for easy monitoring of topographical properties.