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Does a UAS Thermal Camera Measure Heat…No!!!

When people talk about a thermal camera, they mean an Infrared imager. Infrared, commonly abbreviated to just "IR" is a type of radiation similar to microwaves, gamma rays, and visible light. IR radiation is unique in that every object emits it. The hotter the object, the more IR radiation it emits. IR radiation is the heat you feel from a campfire. The human eye can't see IR, but it's everywhere. An IR imager makes it visible by displaying an object’s emitted IR as a color. Objects that don't have much emitted IR may be displayed as blue whereas a hot object with lots of emitted IR may be displayed as red. Think "predator" vision. I'm over 40, so the predator I'm thinking of is hunting Arnold in the jungle of Val Verde and not some species of snakes, but either works. So, thermal cameras don't measure heat; they measure radiation. However, objects with different temperatures emit different amounts of IR. Imagers extrapolate temperatures by measuring IR radiation and display them on the screen. So maybe a better question is, "can I make any money detecting IR radiation?" and the answer is a resounding yes!!!

Professionals who take and, more importantly, interpret IR images (thermograms) are called "thermographers." I've seen thermographers earn up to $200/hr depending on the application. Common applications include leak detection, building quality control, solar panel inspections, and first responder activities. There is a science to collecting the data, but the real challenge is interpreting the image. Let me give you an example. Take a look at the picture above. There is a red thermal anomaly in the middle of the thermogram. Is this a roof leak??? Nope, not at all! It had rained about 6 hours before.

There isn't a visible puddle, but the moisture in the roof membrane aggregate has a different thermal signature than the dry roof. The specific heat of the water and the latent heat of vaporization also play a role. Notice in the same thermogram that the left of the thermogram is green, but the right is red. Why is that? The answer involves a material property called "emissivity." There is a lot to emissivity but for our purposes, it means how well a surface emits IR and how much it reflects it. Now take a look at teh image below. Notice there is a nice purple spot next to the air handler. That purple spot is accurately depicting a cold area (low IR). Notice now that the cold spot is being reflected off the side of the air handler like a mirror. The dirt on the roof is a good emitter of IR, but the metal of the air handler is a good reflector.

The bottom line is this. Infrared imagers are a fantastic tool, and drones are a perfect delivery method. However, you need to know what you're looking at before selling your services. To that end, we will be offering a new "Applied UAS Thermography" online course in July. I teach everything you need to know to understand a thermogram and start using this technology in the class. You'll take the ASNT exam and earn your Level 1 Thermographer certifications as part of the class.

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