Crucial Post-tornado Imagery

The Joplin, Missouri tornado disaster called for emergency search-and-rescue and clean-up missions. A local geospatial services firm responded productively with fast image acquisition and immediate internet distribution.

By Craig Molander

On May 22, 2011, a category EF-5 tornado tore a path of destruction a mile wide across the city of Joplin as it traveled more than 20 miles through Missouri with winds exceeding 225 mph. By the time the funnel cloud had dissipated, more than 150 residents of Joplin were dead, and nearly 10,000 homes and buildings had been completely destroyed, ranking the tornado among the deadliest and costliest in U.S. history.

For Surdex Corp., a geospatial services firm headquartered just a 40-minute flight away in Chesterfield, Missouri, the storm had struck close to home, both literally and figuratively. Several employees grew up in or near Joplin, and many have relatives living in the city. (Thankfully, all were safe.) As news of the disaster reached Surdex personnel on that Sunday evening, the firm realized it was ideally positioned and equipped to support response efforts. Surdex quickly made the decision to donate all flying and mapping services to any interested parties in the Joplin crisis.

Over the next few weeks, Surdex and the local Missouri GIS community learned many valuable lessons about the role of geospatial information in disaster response activities, and the most important was this: It is crucial to collect high-quality imagery as quickly as possible and immediately post it on the internet where tech-savvy emergency responders are waiting for it. The information will be put to use in the disaster zone with breathtaking speed.
 

Flying the Path of Destruction

By the time our personnel arrived for work on Monday morning, a loose plan had already been sketched via emails, texts, and phone calls the night before. We would deploy our Z/I Imaging DMC (digital mapping camera) onboard a Cessna Conquest, our fastest aircraft, to acquire imagery over the impacted area as soon as a suitable weather window opened. The DMC was selected because it can acquire high-resolution four-band imagery at high speed. The original plan called for flying the site twice at altitudes of 2,500’ and 5,000’ above ground level to collect three-inch and six-inch resolution imagery, respectively.

As we waited for the weather to clear, our crews began planning their flight lines. During this process, we made a decision that proved critical to the success of the project. We put word out to the Missouri GIS Advisory Committee (MGISAC) listserv about our plans and asked if anyone had a map of the tornado path. The response was remarkable. Within minutes, the Missouri National Guard and the State Emergency Management Agency (SEMA), both with boots on the ground, delivered remarkably detailed shapefiles delineating the path of destruction.

Early on Tuesday morning, only 36 hours after the disaster, a flight window opened and our aircraft was on its way to Joplin. Acquisition of the lower-altitude, three-inch imagery proceeded as planned just above the disaster-restricted airspace. But as storm clouds again began closing in on the area, the pilot made the decision to ascend beyond the planned 5,000’ altitude to 10,000’ where wider swaths of one-foot imagery could be collected rapidly.

As the aircraft headed back to Surdex base at Spirit of St. Louis Airport, our production staff was preparing to process the data. From 2008 Missouri statewide imagery, they had collected outlines of all major building structures in the area of interest. These would be used in our automated seamline generation software to avoid cutting through building footprints by mistake and creating objectionable artifacts in the final imagery that might confuse responders.

Working with a combination of Z/I Imaging DMC processing software and our own proprietary systems, the production team orthorectified the one-foot images first using the natural color bands and existing elevation data. Once the 40 one-foot exposures had been orthorectified, they were used to filter out some of the three-inch exposures that contained no damage as a means of expediting the remaining processing.

By the afternoon of Tuesday, May 24, we had uploaded the orthorectified one-foot imagery in compressed mosaic versions to a Washington University website commonly used by members of the MGISAC listserv. We also set up our own FTP site for direct downloads of uncompressed files for those who could handle large data sets. We announced their availability via the MGISAC listserv and notified the Department of Homeland Security (FEMA). By midnight, processing of the three-inch ortho-mosaics was completed, and its distribution was carried out in a similar manner.

The imagery spread like wildfire over the internet, and it’s impossible to know precisely how it reached everyone who eventually used it in the disaster zone. But we do know that several state first responder groups that subscribe to the MGISAC listserv were waiting for it. Over the next few days, we sent the imagery to several other organizations, including Microsoft, U.S. Geological Survey, and Esri, to make it as widely available as possible [see sidebar]. In addition, the U.S. Flooding and Tornado Focus Cell of the National Geospatial-Intelligence Agency (NGA) dispatched a courier to Surdex from their St. Louis-area office to pick up a copy of the imagery. The NGA was tasked by FEMA to aid in the disaster response.
 

Putting the Imagery to Work

Because the imagery was distributed for free without restrictions on the internet, we have relied on anecdotal information to tell us how it was used by emergency first responders. GIS offices in Joplin and surrounding Jasper County, as well as the Missouri SEMA, took lead roles in putting printed images into the hands of federal, state, and local public safety personnel shortly after their availability online. Most of this distribution occurred at an emergency operations center set up in the downtown area.

“The imagery became the background map for everything we did,” said Debbie Briedwell, Missouri SEMA GIS specialist. “The image detail was really helpful for damage assessment so the [search-and-rescue] crews knew where to look … and make sure they had all areas covered.”

Chris Chappell, GIS coordinator for Jasper County, explained that a hard lesson had already been learned by command center officials and responders. Wireless transfer of large data sets in and around the impact zone was impossible because cellular antennas had been obliterated. Large-format plotters and printers were pressed into service throughout the region so that hardcopy color prints could be posted in the command centers and distributed to emergency crews.  “The National Guard was printing images and flying them in from 100 miles away,” said Chappell.

Early Wednesday morning when the first prints arrived, search and rescue operations were well under way. The images enabled the commanders to prioritize deployment. One way they did this was to search the images for footprints of large buildings with adjacent parking lots or open fields. In the absence of street signs that could be used to locate specific buildings by address from the ground, this became the quickest way to identify churches and schools that serve as tornado shelters. They were searched first in hopes of finding groups of survivors trapped, but alive, in the rubble.

Red Cross and religious organizations examined the images to find similar buildings still standing so these could be quickly designated as temporary shelters for the thousands left homeless. In all these different applications, emergency responders relied on the images to show them which streets were clear and which were clogged with debris so they could find the fastest route to a priority site.

As is always the case in a major disaster in America, responders from across the country quickly arrived to help, and image-maps were the only resource available for them to navigate the unfamiliar city where landmarks had been wiped out.

“In an area of complete destruction like Joplin, maps were essential to the ground crews,” said Jake MacDonald, cartographer for the U.S. Army Corps of Engineers, Portland (Oregon) District. “Our maps were able to overlay street names and tax lot information on the imagery … so the crews could find their way around.”

Surdex was not the only Missouri organization loading data onto the Washington University website. Just about any public or private-sector entity in the area with geospatial data relating to Joplin seemed to offer it via the MGISAC listserv and post it on an easily accessible website. Some of the applications resulting from the merger of data sets were ingenious.

City and county GIS personnel familiar with Joplin knew that homes in some neighborhoods had basements while others did not. Remarkably, someone obtained a vector layer created for tax assessment purposes that actually differentiated homes by their type of foundation. This was overlaid on the imagery so that public safety crews could focus their searches on basements where survivors might be found. In addition, a state crew tasked with restoring communications draped our imagery over an elevation data set, which enabled them to find the city’s high ground and install temporary wireless antennas there.

As search-and-rescue activities gradually transformed into clean-up and recovery operations, another problem common to disaster scenes had to be dealt with—removing the debris. Thousands of buildings had been torn apart, their materials and contents blown across town in some cases. The remnants of 25,000 vehicles were similarly strewn about and piled throughout the city. Trucks would have to be brought in to gather the debris and move it elsewhere, an unheralded but critical aspect of disaster recovery.

To help with this phase, we deployed our lidar system to fly the Joplin area on Thursday, four days after the disaster. We collected an elevation point cloud with one-meter posting and 15-cm accuracy. We hoped that officials would use this data to calculate the volume of debris so they could determine how many truck loads would be required to move it to disposal sites of sufficient size. At present, however, we have not confirmed that the lidar was applied in this way.
 

Learning from the Disaster

As noted at the outset, Surdex’s involvement in the local geospatial community and participation in the MGISAC listserv sponsored by the Missouri GIS Advisory Council were crucial in distributing the imagery quickly to those who could use it. And the willingness of this community to post whatever relevant data sets they had on an accessible internet portal enabled public safety personnel to create data mash-ups that aided responders on the ground.

The value of providing data to national data distribution portals should not be underestimated. Within a day of processing, we also sent our images to the U.S. Geological Survey for posting on its Hazards Data Distribution System (HDDS), where it was made available along with a variety of geospatial data sets primarily from U.S. government sources. When national or international disasters strike, the HDDS website is often the first stop for FEMA, the National Guard, Red Cross, and state emergency management agencies.

Another lesson learned was the importance of large-format printers. In Joplin, the city GIS office’s plotter could not keep up with the demand for hardcopy images. Valuable time was spent looking for additional printing capabilities in the area. We recommend that every state emergency management office or GIS council keep an updated inventory of printers that can be used in the event of a disaster.

Looking back on the airborne acquisition phase of this event, we realize that timeliness is crucial. If we are able to assist in future incidents, Surdex will fly a single coverage of the impacted area to minimize processing and flight time. Based on the feedback we received from responders who used our imagery, we will split the difference between the three-inch and one-foot imagery and collect only six-inch spatial resolution. This will provide just the right level of detail for search-and-rescue and clean-up missions.

SIDEBAR

Surdex made the Joplin tornado imagery available on its own website at www.surdex.com and also delivered it to these organizations for distribution: Washington University in St. Louis set up http://gis .wustl.edu/Joplin.html.
  • U.S. Geological Survey posted the imagery to its Hazards Data Distribution System at http://hdds.usgs.gov/EO/gis.php.
  • Microsoft Corp., a Surdex business partner, created an interactive before-and-after viewing tool on its Bing Maps site.
  • Jasper County, Missouri posted imagery on its official GIS website at http://beacon.schneidercorp.com.
  • Esri posts relevant imagery and GIS layers for many disasters on its www.arcgis.com site.

Craig W. Molander is senior vice president for business development at Surdex Corporation, headquartered in Chesterfield, Missouri.

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