Thermal Inspections

How thermal imaging works.

Everything warmer than absolute zero gives off infrared. Thermal cameras read the long-wave band, roughly eight to fourteen micrometres. Our eyes can't see it.

It's emitted heat, not reflected light. It works in total darkness, but it can't see through walls or glass.

Inside is an uncooled microbolometer: a grid of tiny pixels that warm up, change resistance, and become an image.

Resolution is low: six forty by five twelve, about a third of a megapixel.

Sensitivity, or N E T D, is often fifty millikelvin or better.

Radiometric cameras store a temperature for every pixel. Non-radiometric ones only make a picture.

Emissivity is how well a surface gives off its heat. Here's one hot plate, half painted, half polished.

The paint reads true. The shiny metal reads cold, and mirrors its surroundings.

So set emissivity for the material.

Distance and humidity soak up signal, and sun-heated surfaces skew the picture. A reading can lie.

Palettes only colour the data. White hot, black hot, ironbow: the temperatures don't change.

Tighten the span and level to make small differences pop.

Timing matters. Around dawn and dusk, objects and background can match. That's thermal crossover, and contrast disappears.

Inspect solar under strong, clear sun. Search for people at night, or when it's cool.

On a solar farm, a faulty cell shows up as a hot spot.

Thermal also finds wet roof insulation after sunset, powerline hot spots, fires, wildlife, crop stress and heat loss.

Fewer pixels means coarser ground detail at the same height. Need detail? Fly lower.

Glass panels reflect like mirrors, so angle the camera off the reflected sun and sky.

Night flying sits outside the standard operating conditions. Check CASA's current rules and your approvals first.

Recap. Thermal sees emitted heat. Emissivity can fool you. Palettes don't change the data. And timing is everything.

Quick check. Same hot plate. Which reading do you trust?

The paint. Shiny metal reflects, so it reads cold.

Visual descriptions

The original narration is accompanied by soft instrumental music.

The animation contrasts visible and thermal views. An illustrated drone thermal sensor uses 640 by 512 pixels and NETD of 50 millikelvin or better. These are example camera figures.

The same hot plate is half matte paint and half polished metal. In the illustrated cooler surroundings, paint appears hot while the reflective metal appears cooler. This illustrates emissivity and reflected radiation; reflective surfaces can also appear too hot in other surroundings.

White-hot, black-hot and ironbow palettes recolour the same data. A dawn and dusk example shows the object and background at similar temperatures, which reduces contrast.

The solar illustration shows a hot spot. Later scenes show thermal applications, pixel size on the ground, reflected sun and sky, and the requirement to check applicable night-flight rules and approvals.

The final check compares polished metal and matte paint on the same hot plate. The choices are polished metal, matte paint, or both. The animation selects matte paint as the more reliable surface in this example.