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Winter 2001/2002
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National Interagency Incident Management Team

Pentagon Damage Assessed with GIS

Even as the inferno continued to rage through the northwest side of the Pentagon, a 39-member group of the select National Interagency Incident Management Team (NIIMT) was airborne, winging its way to Washington, D.C., and the site of the second September 11 terrorist attack.

There are 17 NIIMT teams in the United States, five of them located in California. The primary focus of these teams is wildland fire incident management; however, the teams have been called on to help in the aftermath of other emergencies such as earthquakes, hurricanes, and, now, terrorist attacks.

Composed primarily of experienced professionals from the United States Forest Service and local agency fire departments, team members are operations, finance, logistics, and planning specialists with specific technical skills that allow them to immediately assess emergency situations to determine the manner in which their skills can be best used.

Tim Walsh is a fire captain specialist and GIS enthusiast with the Marin County Fire Department in Northern California. Having served with NIIMT for the past year, he knew exactly what was expected of him upon his arrival at Ground Zero but had to wait a few days for official clearances because of the general confusion and heightened security at the Pentagon following the attack.

Initially obtaining AutoCAD files of the building's blueprints from the on-site contractor, Walsh transformed them into ArcView format and began printing out poster-size floor plans on the plotter provided by Esri's Washington, D.C., office.

"Though we were really just doing graphic reproduction at that point, various agencies, including the FBI, found the floor plans very useful, and it acted as a springboard to doing more GIS-related modeling and analysis," commented Walsh.

One request was from the Department of Defense's Mortuary Affairs section. They had conducted interviews with survivors concerning the last known location of those still missing. Walsh plotted those locations on the floor plans.

Next, the GIS team was asked to analyze and model the structural damage sustained by the Pentagon. By assigning a numeric value, on a scale of one through four, to each supporting column affected by the explosion and fire, workers were able to visually analyze the damage sustained by the Pentagon. Then, said Walsh, the team's GIS technical specialist, Heather Taylor, digitized the damage sustained by each column and then Walsh color-coded the columns according to the numeric evaluation and interpolated the space between each using ArcGrid. The interpolated space was constructed by weighting the value of each column by its distance from the cell being analyzed and then averaging the values. According to Walsh, the resulting model depicted "the most likely trajectory that the plane took as it plowed into the building."

Regarding software, Walsh determined that ArcGIS was an ideal platform to integrate and manipulate CAD files. ArcGIS not only allows individual CAD layers to be turned on and off but also provides transparency capabilities so that grids and other layers can be overlaid onto photo images without obstructing them to allow better analysis.

Technical assistance and equipment were provided by ERDAS, Space Imaging, and Esri to help the NIIMT in their emergency mapping efforts.

For more information, contact Tim Walsh, Marin County Fire Department (e-mail:

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