General Aviation > Aviation in General

FLIR systems question.

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SukhoiLover:
I see, i made this question because i was wondering that for exemple in a desert where during the night the surroundings are really cooled down a FLIR system might detect a heat source much better than during daytime when its really hot and surrounding temperature is higher, possibly close to that of the target ( depending what it is ).

Webmaster:
Hmm, in the desert especially the rocks and concrete radiate retained heat during much of the night, because they have a high thermal mass. So I don't know if it makes as much of a difference in seperating target from surroundings.

Anyone else?

HaveBlue:

--- Quote from: Webmaster on October 22, 2011, 02:25:22 AM ---Hmm, in the desert especially the rocks and concrete radiate retained heat during much of the night, because they have a high thermal mass. So I don't know if it makes as much of a difference in seperating target from surroundings.

Anyone else?

--- End quote ---

I don't know Web, I'm not expert but I might have to disagree here. Any FLIR videos I've seen (cops, border patrol, etc) even in our hot areas like the Texas/Mexico border... the only bright spots are things that are alive. Streets, concrete sidewalks, trees etc are all dark, and only humans, animals and engies light up. I listen to the police scanner on occassion here and our Air One cop chopper never seems to have false hits except in the case of animals (and that one was interesting lol). Just saying.

Webmaster:
I wasn't saying everything therefore lights up, just saying that a 50 degree difference between night and day, doesn't mean a 50 degree difference in all surroundings heat signatures.

The distribution of grey scales is probably dynamic, so you can then have as much contrast for day as night. Upper and lower bounds may also be dynamic, so let's say you have from -30 to 90 degrees at night,  30 to 90 at day. A certain number of shades of grey on the greyscale, let's say 60 for convenience, and uniform distribution (obviously they don't use uniform distributions, as bodies are almost as white as engines most of the time, while pavement/road is way different sometimes, but just for ease let's say it is uniform), so at night 2 degrees per shade difference, day 1 degree. If you have a body temperature of 36 and background of 20 degrees, the difference at day is 16 shades of grey. At night, with your background at 4 degrees, the difference is also 16 shades.

With high sensitivity / better sensors and processing power / better hard+software, I don't see why today's high-end FLIR systems would produce a worse image at day than night to the point where it affects targeting. I think we're way past that and now it's more about resolution/range and maybe additional processing to produce more depth in the image.

That said, I'm out of my depth here...hehe

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