Teachable Moments #4

Outta Control · Feb 25, 2018

Okay fellas, here is the next series to teachable moments.

I always seem to get this question from students about thermal image in water. I wanted to open a discussion on this video and address any question that may arise but before that, you'll notice some interesting occurrences. Such as, why is the water black as ink or what is that residue in the water.

ArrUnTuS · Feb 25, 2018

It's black because its temperature is lower than the animal and the residue is the heat it leaves when it moves?

Maddog · Feb 25, 2018

ArrUnTuS said:
It's black because its temperature is lower than the animal and the residue is the heat it leaves when it moves?

I think you're going to get a gold star on this one!

ArrUnTuS · Feb 25, 2018

I don't know, if he put it on and the answer seems so simple, chances are he has a trick.

It wouldn't be the first time, and so we realize that thermography is much more than it seems at first view

AH-1G · Feb 25, 2018

Ok, here's what I'm thinking, sediment or a type of algae being stirred up?

NorWiscPilot · Feb 25, 2018

I’m concurring with Arruntus.

That beaver’s hot and warms the surroundings ever so slightly.

AH-1G · Feb 26, 2018

If the water is cold why would not the residue heat slowly dissipate? As you watch the video it never or slightly started dissipating.

Unless there was only a slight difference in water temp to body heat?

ArrUnTuS · Feb 26, 2018

Is the otter full of mud? Is she taking a bath to clean herself?

Outta, you're making us suffer

jack.s · Feb 26, 2018

I think ArrUnTuS is correct. The water is coldest so shows black, the lighter water colour is just that it has absorbed heat from the animal. Maybe this is meant to explain something about conduction.An artifact to watch for.

Outta Control · Feb 27, 2018

ArrUnTuS said:
Is the otter full of mud? Is she taking a bath to clean herself?

Outta, you're making us suffer

Ok Ok bear with me on this.

In the thermal world there is nothing colder than a clear sky.

So what you are seeing as the black ink color is actually a reflection of the sky.

Now let's step back a bit and look at this fantastic image.

It was taken from a A8383 thermal HD camera it is a MWIR camera that has a wider range to detect subtle temperature changes and this is where a thermography must understand its subject. Such in this case the Sea Otter's fur.

The Sea Otter's fur has a strong ability to emit heat to keep the animal insulated. So essentially you are seeing a heat signature of the heated water leaving the mammal.

To address the dissipation question, you can actually see the heated water dissipate but at a slower rate due to my past explanation that water retains more heat that most other material.

Finally on the question about can you spot a body below the water. I hope watching the video should be self explanatory and the answer is, No, in most cases, you can not see below any liquids.

Open for comments.

ArrUnTuS · Feb 27, 2018

It's funny how the heat of the animal behaves like a liquid. It is diluted in "water". Thermal exchange is actually taking place there.

The video looks spectacularly good. The camera with HD definition is very noticeable.

Outta, I was expecting a trap

I want more. I'm like a little boy in class

Once again, many thanks Outta

AH-1G · Feb 28, 2018

Congrats ArrUn,

ArrUnTuS · Feb 28, 2018

AH-1G said:
Congrats ArrUn,

Team work

jack.s · Mar 1, 2018

Outta Control said:
Ok Ok bear with me on this.

In the thermal world there is nothing colder than a clear sky.

So what you are seeing as the black ink color is actually a reflection of the sky.

Now let's step back a bit and look at this fantastic image.

It was taken from a A8383 thermal HD camera it is a MWIR camera that has a wider range to detect subtle temperature changes and this is where a thermography must understand its subject. Such in this case the Sea Otter's fur.

The Sea Otter's fur has a strong ability to emit heat to keep the animal insulated. So essentially you are seeing a heat signature of the heated water leaving the mammal.

To address the dissipation question, you can actually see the heated water dissipate but at a slower rate due to my past explanation that water retains more heat that most other material.

Finally on the question about can you spot a body below the water. I hope watching the video should be self explanatory and the answer is, No, in most cases, you can not see below any liquids.

Open for comments.

"So what you are seeing as the black ink color is actually a reflection of the sky."
Ok so are you saying , water is able reflect a heat image?
Also, wondering if the water was shade by say a bridge in part of the image and part open to the sky, what would water look like then?
And by the way thank you very much for taking the time to help us understand a bit. Awesome.

Outta Control · Mar 1, 2018

jack.s said:
"So what you are seeing as the black ink color is actually a reflection of the sky."
Ok so are you saying , water is able reflect a heat image?

In general, yes but in a technical nature, it will reflect the sky regardless if it is day, night, or cloudy condition. Thus why an experienced thermographer, should be able to identify and isolate reflections out of the equation.

Also, wondering if the water was shade by say a bridge in part of the image and part open to the sky, what would water look like then?

It would be the same.

And by the way thank you very much for taking the time to help us understand a bit. Awesome.

you are welcome. I hope you realize that asking these types of question you can have a fairly good understanding of thermography.

John Decker · Mar 3, 2018

"The Sea Otter's fur has a strong ability to emit heat to keep the animal insulated."

Surely if it's keeping them insulated then no heat should escape?

Outta Control · Mar 3, 2018

John Decker said:
"The Sea Otter's fur has a strong ability to emit heat to keep the animal insulated."

Surely if it's keeping the insulated then no heat should escape?

Sure it will. Now I am no marine biologist but like any other mammal it has to be able to regulate its temperature.

Plus you can see for a brief moment how the exposed fur emitted more heat once it went back into the water.

Slade Steele · Mar 3, 2018

Ahhh. Celebrating 2nd law of thermodynamics.

John Decker · Mar 3, 2018

Slade Steele said:
Ahhh. Celebrating 2nd law of thermodynamics.

That law is so old i was sure it had been repealed by now..
No, fair enough Outta, I was thrown more by the wording i think. Keep going with the teachable moments, they're all good. (Even though i struggle to understand how a clear sky can be cold - what about that big yellow thing up there?)

Sojourner60 · Mar 3, 2018

I was guessing otter or seal. I will have to watch this video again. I thought at first it was a fish. I thought I could see it's body as it swam. If you can't see it below the water then that must have been above water.

Thanks for another class! Very interesting. Makes me want to take a class in thermal imaging.