Into the Night

Thermal imaging is effective, efficient airport surveillance technology

Ensuring the safety and security of air travelers and airport resources is becoming increasingly important, and both federal and state homeland security offices are making upgrading and enhancing security measures at airports a top priority. Organizing appropriate surveillance for such a large area is a daunting task for officials and requires an abundance of manpower and cutting-edge technology to ensure thorough protection.

Airports are monitored in a number of different ways, including interior and exterior foot patrols. Typically, augmenting operational security resources are dozens, and in some cases hundreds, of conventional CCTV cameras positioned both in fixed positions and on pan-tilt positioning devices.

Unique Challenges
All airports are situated on maintained, flat terrain with large open areas. Airports also have long lines of sight and are contained by expansive perimeters. In addition, airport construction projects and upgrades are highly regulated and controlled. Upgraded illumination and enhanced tower construction within the air operations areas require, at the minimum, approvals from Federal Aviation Administration prior to installation.

These points make compelling arguments for the use of thermal imaging technology throughout sensitive airport areas as a way to augment existing surveillance capabilities and enhance threat detection to make airports and the millions of travelers safer as they move through these facilities.

The Benefits of Thermal
Use of thermal imaging technology has increased dramatically in the last decade. Predominately used by the military for battlefield situational awareness, the technology has continued to be developed, resulting in increased performance and dramatic decreases in cost. As a result, many non-military users, such as commercial and government aviation and airport authorities, are discovering thermal imaging and the attending benefits.

Thermal imaging cameras, unlike conventional cameras, produce clear video images without the need of illumination and can penetrate fog, smoke, smog, dust and haze. The cameras provide remote video imagery of AOAs and security identification display areas, exposing details of aircraft, automobiles, people, animals and foreign objects on active runways and taxiways as well as the perimeter areas of the airport. Thermal imaging cameras are not adversely affected by airport or aircraft high-intensity lighting and provide a consistently superior image day or night. A wide variety of thermal imaging cameras are commercially available with the same analog and/or digital interfaces as conventional cameras. This allows thermal imaging cameras to be used and interfaced with existing CCTV video command, control, communications, recording and display equipment. However, as thermal imaging technology is relatively new to the commercial marketplace, and to the commercial user, there are important basic technology terms to understand.

Imaging Technology and Terms
All objects emit infrared energy. Infrared energy is just one part of the electromagnetic spectrum that encompasses radiation from gamma rays, X-rays, ultra violet, a thin region of visible light, infrared, microwave and radio waves. These are all related and differentiated by wavelength.

Generally, the higher an object's temperature, the more infrared radiation it emits. Thermal imaging cameras detect this radiation in a way similar to the way an ordinary camera detects visible light. Images from thermal imaging cameras are monochromatic because the cameras are generally designed with only a single type of sensor responding to the infrared radiation wavelength range. Within the infrared wavelength band, two distinct IR wavelengths pass effectively through air:

• Mid Wave IR (MWIR) - ~3 to 5µm

• Long Wave IR (LWIR) - ~7 to 14µm

Thermal imaging cameras can be readily distinguished by the detector type contained within the camera. Essentially, two sensor types -- cooled and uncooled -- are available. Cooled detectors typically are sensitive to MWIR radiation. They are contained in a vacuum-sealed case and cryogenically cooled. Without cooling, these sensors<\m>which detect and convert energy in much the same way as common cameras but by using different materials<\m>would be "blinded" or flooded by their own radiation. Thermal imaging cameras are more expensive than uncooled cameras. However, cooled infrared cameras provide superior image quality and can detect, recognize and identify objects at great distances -- up to 10 miles. Uncooled thermal cameras typically are sensitive to LWIR radiation and use a detector that operates at ambient temperature. As they do not have cryogenic coolers, uncooled thermal imaging cameras are smaller and less costly. However, resolution and image quality are lower than cooled detectors. This is due to difference in fabrication, which is limited by currently available technology. They also are effective in identifying objects at distances less than 2 miles, with many having smaller focal length lens<\m>less than 100 millimeters<\m>that are effective to half that distance. Which is better: MWIR or LWIR thermal imaging cameras? Frankly, there is no easy answer, as the choice is dependent on the following factors:

• Site geographic location/climatic conditions

• Overall atmospheric transmission

• Source temperature

• Solar effects

• Target range

In general, the following thermal imaging types are preferable at sites with the following site conditions:

Detector Type
High Humidity
LWIR (<2.5km), MWIR (>2.5km)
Arctic / Subarctic
Average Climate
Smoke / Aerosols
High Temp Targets
Target at Long Range

Airport Solutions
A few cooled MWIR long-range thermal imaging camera systems, with integrated programmable pan-tilt positioners, can be situated at locations where line-of-sight is at an optimum, such as on air traffic control towers, easily providing surveillance coverage for the majority of the AOA, SIDA and airport perimeter fence boundaries.

These systems can be readily slaved to alarms from other sensors, providing authorities and air traffic controllers with continual day and night sensor assessment situational awareness covering most of the airport and extending outside the airport perimeter. The pan-tilt would quickly respond to alarm or command, allowing automatic and quick azimuth and elevation position changes to point thermal imaging cameras and optional long-range visible cameras to the alarm location. In non-alarm conditions, the system programmable autoscan can automatically position the thermal imager and optional visible camera in a set scanning pattern. Aircraft, cars, people, animals and foreign objects can be detected, identified and recognized at greater distances, day or night, through most smoke, smog and fog. The overall system configuration could be augmented with uncooled LWIR short-range thermal imaging camera systems and would be situated in locations providing surveillance coverage in areas blocked from view from long-range MWIR systems. These systems also can be readily integrated in the same fashion as their long-range counterparts. Thermal imaging cameras can be easily interfaced with existing and new CCTV video command, control, communications, recording and display equipment for monitoring at centralized and distributed control facilities, providing effective and efficient surveillance of airport areas.

Thermal Imaging Solution Advantages
The number of thermal imaging cameras needed to provide airport-wide surveillance would be considerably less than the need for conventional cameras and with markedly improved, clearer images no matter what lighting is available and regardless of visibility. As a result, the total cost of ownership for an airport thermal imaging wide-area surveillance system is far lower than conventional CCTV systems.

Beyond providing improved airport security and safety, airport operations also find that thermal imaging provides enhanced operations and situational awareness of snow-plowing operations, airfield lighting inspections, runway and taxiway foreign object detection, runway incursions, emergency response, bird and hazard monitoring, environmental monitoring and contractor escort operations. Airports are critical to a region's trade and transportation capabilities. Providing safe and efficient travel is of the highest priority and enhances everyone’s well-being. It is important to continue to evaluate and improve airport operations systems. The application of commercial thermal imaging technology at airports offers dramatic improvements to security, safety and general surveillance operations while reducing overall operational costs.

This article originally appeared in the January 2009 issue of Security Today.

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