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Help me understand

LonelyDad 🚫

Given: everything with a temp above absolute zero give of IR. The higher the temp, the more IR. What I am having a hard time understanding is stories where IR is used to see inside buildings to locate targets, and track their movement. Let us take for example a standard home. The exterior walls are typically a half in of stone (drywall), three inches of insulation - usually fiberglass, and an exterior wall of possibly 1/2" clapboard, with maybe a layer of metal or plastic siding. Yet in the stories one is able to not only locate, but track in real tome human and pet locations and motion. to my mind, in order for the IR from a human to be able to be sensed through all that their body would have to be giving off so much IR that they should be dead from heat stoke. I will grant sensing through a pane of glass or clear plastic, but have a hard time accepting tracking motion through standardly constructed outer walls.

Replies: Dominions Son Pixy samt26 NC-Retired oyster50 Paladin_HGWT alaska Mushroom

Dominions Son 🚫
Updated:

@LonelyDad

There may me materials that are opaque to visible light that are transparent to IR. That said, exterior walls of a building should not be. I would think that would defeat a good chunk of the insulation value.

That said, even at normal body temps, IR emitted by a human body would marginally warm the interior surface of the wall which would eventually make it's way to the outer surface increasing it's IR emissions.

However, I would think like a light bulb, the IR from a human body would illuminate the entire wall. Which would not give a clear outline of a human body from the outside.

This seems to support my thoughts.
https://www.processparameters.co.uk/can-a-thermal-camera-see-through-walls/

Replies: Vincent Berg

Vincent Berg 🚫

@Dominions Son

From what I understand of it, is that you can't see any details one a human or animal's body from that distance with those obstructions. I'm a bit confused by the term "stone dry wall". The only dry wall I've worked with (U.S.A.) has no stone in it at all (I'm familiar with this, because I've put my fist through most drywall walls a few times in the course of my life).

In those situations described, you'd see a fuzzy outline no details (and when does TV or movies not show every detail?). Thus IR (Infrared light) all you're seeing is heat, so there'll be a firmer edge, yet with the distance and obstructions, no precise details at all.

So instead of those visuals of the beautiful young action star, consider the ones you get of a night-time sniper with a IR-scope. In most of those situations (in film) all you see is a mostly blurry image. So you couldn't even determine if someone picked up a ball, though you would if they pet a cat or a dog.

A large building is entirely different, as those contain a LOT of steel and stone and the walls are much thicker, so it's more like 5G internet, where you can pick it up if you're in an exterior office with a window, but wouldn't if you're an inner office.

@Sam26 offered the best description so far.

Replies: LonelyDad

LonelyDad 🚫

@Vincent Berg

Sorry, should have been drywall, which is made of a layer of gypsum between two sheets of paper. The last I heard, gypsum is made from stones.

Replies: Dominions Son Vincent Berg

Dominions Son 🚫
Updated:

@LonelyDad

Sorry, should have been drywall, which is made of a layer of gypsum between two sheets of paper. The last I heard, gypsum is made from stones.

I saw somewhere recently someone saying that both Drywall and Sheet Rock are brand names of gypsum board.

Replies: palamedes

palamedes 🚫

@Dominions Son

I saw somewhere recently someone saying that both Drywall and Sheet Rock are brand names of gypsum board.

Drywall is not a brand name. It is a material made of gypsum, which is installed without using water. Drywall is also known as plasterboard, wallboard, gypsumboard, and Sheetrock (a brand name). Sheetrock is a popular drywall brand made by U.S. Gypsum Corporation and also made of gypsum. Augustine Sackett invented the earliest incarnation of what we call drywall in 1894 and was called Sackett Board.

Vincent Berg 🚫

@LonelyDad

Actually, you're right, only the gypsum is 'crushed', pulverized rock, which I suspect is mixed with something softer, or I'd have crushed my hand, anytime I was stupid enough to punch it. They key with drywall, is that it needs to be soft enough to be cut, either with a reciprocating saw, or often with a simple Exacto knife (when you need to cut out the holes for electrical outlets of light switches).

Replies: bandeau_rouge

bandeau_rouge 🚫

@Vincent Berg

ive been in a gypsum mine before. It was like greasy chalk.

Pixy 🚫

@LonelyDad

The majority of internal walls are not insulated and given the minimal legal dimensions for windows, you could easily follow a persons progress via windows. Granted, the person with the IR imager would have to move around a lot to keep LOS with the target. In tall buildings, this would not be practical unless the imager was on a drone.

samt26 🚫

@LonelyDad

Thermal radiation is electromagnetic radiation (light-photons) spanning all frequencies. Thermal radiation can't see thru normal walls - and glass is an especially good reflector. Thermal radiation characteristics are somewhat dependent on its frequency - some frequencies are absorbed by rain, or fog, for instance. The sensor quality has improved greatly over the years, especially in sensitivity. It is very useful in clear atmospheric conditions.

NC-Retired 🚫

@LonelyDad

Don't know if this will help or confuse.

https://youtu.be/poxz9awohQs?si=8f_QT5H1hsKE7-VX

Search yewtoob for thermal and infrared and there's some ads and lots of vids that might help.

Replies: FantasyLover

FantasyLover 🚫

@NC-Retired

Not an expert, but read once some time go that Hollywood is responsible for us thinking that IR images are visible through walls and that ground penetrating radar clearly shows buried skeletons and whatnot.

oyster50 🚫

@LonelyDad

IR surveys was part of my career over the past forty years. I couldn't see through walls.

I still have a camera.

oyster

Paladin_HGWT 🚫

@LonelyDad

What I am having a hard time copesunderstanding is stories where IR is used to see inside buildings to locate targets,

Those "sights" "scopes" etc. are not using natural IR light, but instead are using an IR light that illuminates an area to be seen using an IR viewing device.

Back in the late 1940's through the 1980's, many tanks had an IR "searchlight" mounted above the main gun (cannon). Most also had IR headlights next to the regular white lights, that the driver could see using an IR periscope mounted in his hatch.

These were common on tanks and other AFVs in the armies of the USA, UK, West Germany, and other NATO nations, as well as Japan and Australia.

The Communist nations understood the technology, but it was too expensive to mount on all of their tanks and other AFVs (at first). Moreover, the technology was a bit "finicky" and sometimes broke down, more so to USSR and Communist Chinese vehicles.

By the 1980's most NATO nations understood that enemies were likely to see Your IR lights.

...but since the 1960's the USA had been deploying practical "Light Intensification" goggles, sights, etc. "Starlight Scopes"...
They didn't need much light, but in "total darkness" in particular inside tunnels, buildings, etc., you needed a small IR light.

Replies: moondog_199 samt26

moondog_199 🚫

@Paladin_HGWT

Good summary…
And to follow on from your final line (for the wider audience), current weapon mounted laser designators have an option for IR laser and a broader " beam" of IR to use as a light source for Night Observation Devices. Not quite like Hollywood magic for IR or thermal images though.

samt26 🚫

@Paladin_HGWT

The sensors stopped needing external light amplification beginning in the 1980s. The sensor send the thermal radiation within objects - at night, as the atmosphere cools, the radiation is even more visible to the sensor.

alaska 🚫

@LonelyDad

I asked the AI Grok the question and was given a long answer but for the purpose here I only provide the conclusion "For users expecting IR detectors to function like movie portrayals, where characters see through walls with thermal imaging, the reality is different. The technology is limited by physics, and while it can detect surface heat, it cannot provide the through-wall visualization seen in films. This is a common misconception, as noted in Teledyne FLIR, which addresses popular media misinformation. Users should be aware that for through-wall detection, radar systems are the go-to technology, not IR, which might be an unexpected but crucial detail for understanding the technological landscape.

Replies: Paladin_HGWT

Paladin_HGWT 🚫

@alaska

I only provide the conclusion "For users expecting IR detectors to function like movie portrayals, where characters see through walls with thermal imaging, the reality is different. The technology is limited by physics, and while it can detect surface heat, it cannot provide the through-wall visualization seen in films.

Not "IR" (Infrared); Thermal viewing devices may be able to "see" through solid objects, including walls, and many other objects/materials (but not all).

The heat of a vehicle engine is easier to detect, than a living human body.

Often a computer "enhances" the image.

You can go to YouTube and see videos of an AC-130 "Specter II" engaging targets, seeing a screen using enhanced Thermal viewers.

Mushroom 🚫

@LonelyDad

What I am having a hard time understanding is stories where IR is used to see inside buildings to locate targets, and track their movement.

Most really do not know how such things really work, so take what they believe from movies.

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