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• Accident investigation. Traffic accident re-constructionists often begin measurements from the start of the first visible skid mark in an effort to determine speed at impact. Modern cars equipped with anti-lock braking systems are designed to not leave such marks; however, rapidly slowing a vehicle, even with no visible skid, requires huge amounts of friction between tires and pavement. This friction leaves thermal signatures that can linger for longer than you might think. Although many variables come into play in determining how long these marks would be visible, a fair estimate may be 30 to 45 minutes post-crash.
Ever found a vehicle wrapped around a tree or in a field, but with no one inside? Ever used a thermal imager to search the surrounding area for victims who might have stumbled from the wreck only to collapse from their injuries several hundred feet away? Or, better yet, as one police department found, ever found an intoxicated driver who climbed the tree that he wrapped his vehicle around in an effort to avoid apprehension? In searching the surrounding field for victims and finding none, officers returning to their cruisers spotted a large white object in the tree immediately above the wreckage. There they found the driver, too intoxicated to flee, who had climbed the tree to hide from police.
• Search and rescue. How many times have you been sent to look for a child who ran away from home? How about a senior citizen afflicted with Alzheimer’s? In both circumstances, we are rarely called to the scene as soon as it happens. Usually, the family will search until dark and then call 911 when their efforts fail. With a thermal imager, you can cover large areas in short order. Depending on the manufacturer, you can see up to three-tenths of a mile in any direction. That’s a search circle over a half-mile in diameter.
The thermal imager as a primary search tool
Large fields, parks, roadways and wooded areas are all easily searched with a thermal imager. Creeks and streams also offer a unique use for thermal imaging. Ever worked in the rain around swollen creeks or streams looking for someone thought to have fallen in? Ever responded to a pond, lake or ocean on an overturned canoe or boat? One characteristic of water is that it usually looks very cool to a thermal imager. Victims, on the other hand, appear very warm. This makes for a bright white object on an otherwise dark gray/black field of view. Stop using the flashlight as your primary search tool. It can safely be moved to secondary. Put the thermal imager up front. Use it to search these bodies of water.
• Disturbed surfaces. The theory behind disturbed surfaces is that once an otherwise uniform surface has been rendered non-uniform, it can never be made to appear uniform again. I know what you’re thinking…huh? Let me explain it this way: criminals may take a metal shipping crate that the large cargo haulers use and torch a hole in the side of it, build a false wall, stuff it full of contraband, weld the cover back on, sand the weld and repaint the surface so that it appears as if nothing has been altered. To the eye, all appears normal. To a thermal imager, the weld, sanding and repainting can be seen because of the difference in the way that metal wall absorbs and radiates heat. This difference is visible to the thermal imager. Altered drywall? Visible. Overturned earth or recently buried areas? Visible. Body fillers and putties as used in the hidden vehicle compartments? All visible to thermal imaging.
• Locating evidence. Concealed weapons tossed during a foot pursuit, firearms thrown from moving vehicles, drugs discarded and even recently handled empty beer cans in a vehicle will all generally yield a latent thermal image. Some objects, like recently fired weapons, display a much stronger thermal image than others; however, having the ability to detect and recover all evidence not only aids in the investigation, but ultimately better serves the public.