When the Polk County, Fla., Fire Department responded to a fire raging at a local plastic factory in 2004, thick smoke obscured much of the view. Ordinarily firefighters are left with risky guesswork -- the size of the building is unknown, entrances are obscured, and tanks that might contain highly combustible material are hidden -- but from the laptop in his command car, Polk County Fire Chief Doug Lewis pulled up clear, aerial images that provided unobstructed views of the building from several directions. These images, taken at oblique angles, allowed him to assess the most effective and least dangerous way to fight the blaze.
On March 12, 2005, Gwinnett County, Ga., police closed in on Brian Nichols, a detainee who shot four people in a rampage at a courthouse the day before. Worried that aerial surveillance might alarm Nichols, who was hiding in an apartment building, the county's SWAT team opted for oblique images of the complex to plan the gunman's capture.
The images allowed the police to get aerial perspective of what they couldn't see from the ground, such as the location of garages, trees and other buildings, which could be used for cover.
Although oblique imagery has been around for a long time, only recently have such success stories made it a popular instrument in the emergency management community. As a result, there has been a surge in use of oblique images by police, fire and emergency response teams at the local, state and national levels. This surge has allowed more people who understand public safety, but not technology, to use tools that can better help them do their jobs.
"The beauty of [oblique] imagery is the way it helps mayors, fire chiefs and the public understand what they are looking at," said Art Kalinski, GIS manager of the Atlanta Regional Commission (ARC). "The use of GIS at ARC has grown from 30 users to more than 420 since we started using oblique imagery."
Merging Software With Images
Public safety experts consider oblique images more valuable than ortho images, which are top-down, distortion-free, highly accurate photos, ideal for mapping purposes. Because of their accuracy, ortho images have been easy to integrate with GIS.
But as Kalinski and others have discovered, ortho images are hard to understand when viewed by nonprofessionals. "Orthos are very accurate, very specific," he said. "Oblique images aren't as accurate, but public safety doesn't need such a high degree of accuracy."
What oblique images do provide is perspective -- lots of it.
Buildings can be viewed from numerous angles, rather than one vertical view. More importantly, recently developed software tools let users measure and analyze what they're viewing.
Pictometry International Corp., a digital and oblique imagery firm, developed software that can measure height, length and width of buildings, as well as their elevation. Polk County's 911 service became the first in the country to link oblique imagery with its mapping software. When an emergency call comes into the county's communications center, Pictometry's Electronic Field Study software integrates the caller's location coordinates with an oblique image as well.
Another Florida-based company, Aerial Cartographics of America Inc., provides similar services with Multivision, a viewing and measuring tool that integrates oblique and aerial images.
These types of integrated imagery systems, of which there are few, are particularly appealing to public safety agencies, according to Will Smith, Pictometry's marketing manager. The firm has contracts with more than 200 government customers, with public safety agencies making up the largest segment.
Because of the rich variety of angles of one location it provides, oblique imagery could be mistaken as costly; but government officials, such as Kalinski, assure it isn't terribly expensive. Pictometry offers its customers as many as 12 perspectives for each geo-referenced image, and bases its prices on the square miles covered and level of resolution, according to Dante Pennacchia, chief marketing officer. The company offers customers a choice of either high-resolution images at 1.5 feet per pixel or standard images at 6 feet per pixel.
In the case of Polk County, the 911 center has access to 63,000 high-resolution images from 12 different angles that cover the county's 2,000 square-mile jurisdiction. In addition to allowing the fire department to measure objects and buildings, dispatchers can use the images to assign alternate traffic routes to incidents, scope each address from multiple angles for entry and escape routes, and provide guidance on the location of electrical wires and other obstacles that might obstruct rescue equipment or helicopter access.
Dispatchers also find the images useful when police or emergency crews are responding to a nighttime incident. Often, first responders will drive by the location because it's hard to identify a building or house in the dark. With oblique images, dispatchers can provide details that police and firefighters can't see. When the images are linked with GIS, the dispatchers can give address coordinates as well.
Time Critical
With the spate of large-scale disasters -- manmade and natural -- in recent years, emergency management has turned increasingly to aerial imagery to provide support during disasters, and help assess damage and recovery afterward. Professor Jan Husdal of the University of Utah points out that images play a role in documenting what actually happened. In a paper published in 2001, Husdal wrote, "Taking air photos during a disaster will not only preserve the scene of an emergency, it will provide information on the damage extent and foretell what to expect the next time a disaster strikes."
This was certainly the case with Hurricane Katrina. Months after the disaster, newspapers and magazines continue to publish before and after aerial photos of the levee breaks as debates continue over repair and replacement.
Because of ARC's extensive experience merging GIS with oblique imagery, the Atlanta agency played a significant role during the crisis by overlaying geographic coordinates onto images of the Gulf Coast provided by Pictometry. These images were hand delivered to first responders in the region.
One significant feature of Pictometry's software is its Change Analysis tool, which allows emergency management teams to analyze before and after photos of the same location. This feature can be particularly useful for government officials who must quickly but accurately assess damage from a disaster.
Nobody knows the importance of speed and images better than Ron Langhelm, the Federal Emergency Management Agency's (FEMA) GIS coordinator for its region 10 response operation located near Seattle. Langhelm conducts disaster assessments using GIS and imagery, as well as other data. He typically investigates the impact of earthquakes, fires, and heavy snow and rainstorms on the region.
But Langhelm is also a member of FEMA's national emergency response team. As the team's technology specialist, he has covered the biggest disasters to hit the United States in the past eight years, including 9/11, the Space Shuttle Columbia tragedy and Katrina.
According to Langhelm, each disaster presented a unique challenge. "The Trade Center attack was a massive disaster in a confined area," he explained. "The Columbia explosion was the opposite: a small amount of debris spread over a huge area. And Katrina was a combination of both: a huge disaster covering a large area."
But regardless of their nature and scope, all disasters require quick decision-making based on reliable data. "Working in a disaster means getting your hands on the right data as quickly as possible. Time is critical," said Langhelm, who first used oblique images during 9/11.
"Oblique is good for specific sites," he continued. "It allows you to get a good estimate on a structure's dimensions, the square footage, the access points."
However, working with oblique images requires human interaction, whereas satellite photos of disaster sites can be computer analyzed for data. "I would say that oblique images support tactical decision-making very well," Langhelm said, "but it's less useful on the operational side."
Tactical use helps with immediate, short-term concerns. For example, when cops visited the flooded streets of New Orleans right after the storm, they couldn't identify the houses. But with the oblique images integrated with GIS, a dispatcher could tell them what they were seeing.
The operational use of oblique is more strategic, and for long-term purposes. Emergency management officials can use the before and after oblique photos to assess damage and cost of repair, as well as evaluate plans to rebuild versus demolish damaged property.
Images by the Terabyte
An early criticism of aerial imagery has been the large size of the image database -- for ARC and the 10-county region it covers, its image library is massive, Kalinski said. But with the continuing decline in data storage costs, the size of a digital image database is less of an issue. Recently ARC added three terabytes of storage to its existing capacity, and has purchased numerous 500 GB portable hard drives for file transfer and field operations.
Kalinski also suggested that the cost of oblique imagery is relatively reasonable considering its multiple uses (see Not Just for Emergencies). The property assessor for Gwinnett County -- one of the counties in ARC's region -- originally planned to photograph the fronts of all properties in the county for $850,000, but got far more coverage from the multiple aerial angles offered with oblique images for around $350,000.
In at least one instance, the federal government has also stepped in and helped cover the cost of oblique imaging for local governments. In January, Congress granted $1.1 million to map seven counties in upstate New York. Pictometry will use the funds to create a regional database of oblique images for use by law enforcement and public safety agencies in the area.
Whether that grant is the start of something new in terms of federal support for this technology, or just an exception, remains to be seen. But based on the growing use of oblique images worldwide and their impact on emergency management operations, we're likely to find high-resolution, oblique images -- and the software that makes them so useful -- more accessible than ever.
