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Imaging a disaster

Photonics Spectra
Dec 2008
Laura Marshall,

It started with a request from the Centers for Disease Control and Prevention. The CDC was looking for two unmanned aerial vehicles (UAVs) to shoot images of disaster areas.

But the way David Price tells it, as soon as he heard about the request, he was hooked. And all because of his favorite hobby.

The senior research technologist at Georgia Tech Research Institute (GTRI) is a radio-controlled airplane enthusiast. As a kid, he and his brothers flew model rockets with their dad, but Georgia Tech colleagues got him hooked on planes. “All of the engineers on the project are R/C pilots and electronics designers,” Price said.

The Mini ModPOD is the white box attached to this helicopter. It is a low-cost, high-resolution imaging system developed by Georgia Tech Research Institute researchers that creates a detailed picture of an area devastated by a hurricane or other natural disaster. Photos courtesy of Georgia Tech Research Institute.

The UAVs were needed to count disaster refugees, and the project is Benjamin Sklaver’s baby. Sklaver, program analyst for the International Emergency and Refugee Health branch of the CDC, said he could be considered the ModPOD project manager. After all, he’s been working on it for about nine years.

“[My] office in general is responsible for providing technical assistance to the CDC and the US government and international nongovernmental organizations during complex humanitarian emergencies,” he said. “My specific piece involves demographic assessment. One of the big challenges is rapid population assessments in displaced-person settings.” The assessments allow agencies to determine how much food, water, medicine or other aid will be needed in the area.

The CDC worked closely with the GTRI team. “We dreamt it up, and together we figured out how to do it,” Sklaver said. “They’re smarter engineers than we are.”

But they didn’t get very far before an actual disaster struck: 2005’s Hurricane Katrina.

In the days that followed, Price said, airspace safety concerns grounded UAVs in the New Orleans area. It didn’t make sense to build unmanned vehicles if they would be banned during an emergency situation, so the team switched to a small portable system that could be attached to a helicopter and dubbed the system the Miniature Modular Photographic Observation Device, or “Mini ModPOD.”

The most vital component was the camera itself.

Price compared it with Google Earth, which provides dramatic close-up aerial satellite views at about one pixel per foot – “not close enough to see faces,” he said.

The off-the-shelf camera chosen for the ModPOD was a Canon Digital Rebel XTi, which offers 64 pixels for every one pixel in a Google Earth image, meaning that the ModPOD images would be “64 times better,” according to Price.

This mosaic image is made of individual photographs collected from the Mini ModPOD system and stitched together using computer software to create a more complete picture of the ground below.

ModPOD pictures are “near-real time,” he added. “As soon as the skids touch the ground and the guy says it’s OK to open the door, and you can take the memory card out of the camera – 30 minutes later, you have your photos.”

Sklaver agreed. “The speed at which we can get these images is just unmatched.”

A global positioning system (GPS) receiver stores time data as well as time-space position information, Price said, so the user can pinpoint when and where a photo was taken. Users also can define a zone of interest and program it into the system. “When the GPS reports we’re in that zone, it starts snapping. That way, we have a constant 60 percent overlap.”

That overlap is necessary for the CDC to use Leica Geosystems AG’s Mosaic CuePac from Erdas Inc. of Atlanta to create an overall picture of the affected area by stitching together individual photos.

Researchers Gary Gray, left, and David Price insert a USB drive loaded with mission parameters into the Mini ModPOD imaging system. The system will estimate the number of refugees after a natural disaster and assess the need for health and humanitarian services.

Other essential ModPOD elements include a circuit board that uploads mission parameters; an inertial measurement unit that tracks the aircraft’s rate of acceleration plus changes in pitch, roll and yaw; a lithium polymer battery; and a switch that fires the camera shutter from inside the helicopter.

There is no doubt that the GTRI engineers had fun designing and testing their Mini ModPOD. “I’m happy to report I got to ride in a helicopter. That was a first for me,” Price said proudly.

But they never lost sight of the goal: helping disaster victims. “We’d like to think that this will be put into use,” he said, “and that there might be somebody standing out on a roof somewhere and this could get him the help that he needs.”

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