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Night Vision Thermal performance weather conditions affect

Phantom223

Sergeant
Full Member
Minuteman
Feb 7, 2012
221
2
50
Oklahoma
I thought I would share a experience from this weekend. I’ve been using thermal imagers for a couple years now and know how weather conditions can affect your overall image performance. However this week we had some rain and a cold front pass through later that night my thermal scope and mono’s image clarity looked horrible! It was the worse I have seen since using thermal the last few years I mean it barely worked to provide a useable clear image and only at shorter rangers. In fact I thought something was wrong with my thermal mono until I checked my thermal scope and it look horrible also. Both were FLIR 336 cored systems and I checked my HD19s it also struggled to provide a good image

I went to my PVS-14 head mount and IR laser for the rest of the evening it looked great with the moon out super clear image. I’m not sure what about the weather conditions gave such a negative effect to the overall thermal performance as I have looked through solid fog and had a much better image even then?
 
I think allot of it has to do with whether or not the sun actually made it out during the day to warm things up, if not everything is monothermal surface wise, except of course for a hog or a coyote...which often makes them stand out even more, although range will be limited.
 
High humidity will negatively effect most thermal units. However, my L3 LWTS is unfazed by high humidity. My FLIR T50, T60 and M18 struggled in high humidity. The LWTS is an amazing thermal unit in all environments that I have tested it.
 
We hunted last weekend (I say hunted, we walked around shooting armadillos and whatever else we found) and it was 90ish degrees and very, very foggy. The thermal struggled some, but you couldn't see far at all with I2, and our lasers looked like 55 gallon drum sized beams in the air. When the sun hasn't been out for days and it's cool and clear, it can be the opposite. In hard conditions for thermal, lens size plays a big part. Bigger, better.
 
We hunted for two days in the middle of a tropical storm wit 50mph winds, torrential rains, and summer heat, no one killed anything besides me with my FLIRs, NV was useless...


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Yep, I have always found thermal to work when NV wouldn't in the past. We get alot of settled fog in our bottom land during late summer/fall it shuts down NV use, but thermal will see right through it no problem. This weekend was the first time ever that my NV worked well and my Thermal wouldn't. I think Skypup hit the nail on the head rain cooled everything down,no sun came out to warm anything, so when dark everything but living critters was basiclly the same temp making a flat/no contrasting image. One bad night in 3 years of using thermal so I can live with that :)
 
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I hate it when that happens, then it is even difficult to differentiate the horizon from the sky, making it a puzzle to find out where the ground actually is...
 
I've seen this also it happened when we did the thermal review. Hot, humid, off and on rain then a cold front hit and temps dropped. My conclusion was the moisture retained heat better than the air around it creating a fog the thermal could detect.
 
Cold, overcast, windy conditions completely suck using thermal! The first time this happened to me I was in south texas, and I thought my 307 was messed up. Looked threw a weapon sight and I experienced the same thing. Image quality was great right after dark from a little sunshine , however the cold wind after 4 or 5 hours equalized temps of everything. You literally couldn't tell if you were looking down a sandero or looking into the brush. No issues with nvd's.
 
Cold, overcast, windy conditions completely suck using thermal! The first time this happened to me I was in south texas, and I thought my 307 was messed up. Looked threw a weapon sight and I experienced the same thing. Image quality was great right after dark from a little sunshine , however the cold wind after 4 or 5 hours equalized temps of everything. You literally couldn't tell if you were looking down a sandero or looking into the brush. No issues with nvd's.

This is where fusion / dual-band imaging is king.

If the sun doesn't come out for an entire day or more, this further compounds the cool and wet (or humid) and windy conditions which degrade the thermal imaging. Also, tropical environments where everything is heated to high temperatures and rained on up to several times a day are equally challenging to thermal sensors.

The FLIR thermal scopes often seem to wash out more than the Insight thermal scopes, in the above conditions, whereby a human for example in heavy fog will show up clearly as a warm body but everything around it will appear as a white-out. The FLIR thermal cores are actually picking up much more thermal detail than your eye can distinguish, but the image management is designed to focus on highlighting the warm body vs. cooler background contrast -- as a result, the thermal signatures of the background detail are midpoint equalized. This effectively highlights the warm body against a "blank" canvass to maximize detection. However, this comes at a cost of losing the identification of things in the background that give the contextual clues needed for activities such as navigation.

When this approach is applied to fusion imaging, where the "blank canvass" is completely eliminated from the thermal view, and only the highlighted warm body is super-imposed onto the night vision image; you get the best of both sensor technologies. Many novice users of the COTI and ENVG will complain, initially, that they can't get thermal highlights of trees and other contextual, environment details. That is because the image management on these devices is coded to cut out the thermal noise. Otherwise, the firmware can be adjusted to thresholds where the very useful "outline mode" will put a thermal outline around every single object in the field of view. For demo purposes, there is a definite wow factor to this. However, it isn't useful to have everything in the field of view and their details outlined, whereby (for example) the outline of a set of warm footprints on a sidewalk becomes completely lost in the noisy outlines of all the cracks and embedded stones in the concrete.

FLIR is much more invested in dual and multi-band imaging than Insight / L3 / Eotech, which is much more mono-band focused. Therefore, in their LWIR scopes, Insight codes their image management with algorithms that do more to present and equally highlight the thermal signatures of background and contextual details. While this gives a much more pleasing and versatile experience to many customers seeking to try to leverage their one thermal only scope for both detection and identification, it actually impedes detection and interferes with identification in the dual band / fusion application. The ADUNS has pretty much the same thermal image management algorithm that is in the T-60, T-70, T-75, and when it is fused with the night vision / light intensified imaging, the results are outright eye-popping. This is headed someplace for future product capability that I really can't go into the details about.

Thus, all this to say that there is more than what meets the eye in regard to what FLIR and Insight are investing in with their different approaches. Both actually are not interested in duplicating what the other is doing well. They have some overlaps in the market space, but generally they actually do have different niches of capability they are pursuing.

IR-V
 
Hi IR-V, thanks as always for your valuable input. You opened your comment with with fusion / dual band imaging. Correct me if I'm wrong but these devices such as the ADUNS, etc. are hybrids per say? They overlay their respected images onto each other, "super-imposed" as you mentioned. TRUE fusion are things we're seeing from folks over at INTEVAC where they actually use a Photocathode without the MCP (low noise/miniscule halo) with a digital output enabling true fusion when used in conjunction with a thermal sensor. I know these are VERY complex systems I am describing and technically (I'm no PhD), know just enough only to have worn a few in my past travels and see some pretty significant results.


Vic
 
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I don't think ADUNS uses a vanadium oxide uncooled micro bolometer either, slightly different wavelengths.


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Hi IR-V, thanks as always for your valuable input. You opened your comment with with fusion / dual band imaging. Correct me if I'm wrong but these devices such as the ADUNS, etc. are hybrids per say? They overlay their respected images onto each other, "super-imposed" as you mentioned. TRUE fusion are things we're seeing from folks over at INTEVAC where they actually use a Photocathode without the MCP (low noise/miniscule halo) with a digital output enabling true fusion when used in conjunction with a thermal sensor. I know these are VERY complex systems I am describing and technically (I'm no PhD). know just enough only to have worn a few in my past travels and see some pretty significant results.


Vic

Hello Vic. That is correct - ADUNS is overlay and not actual fusion of the image planes at the capture level. But, there is a certain opportunity to be had with the overlay approach for modular integration that the user can configure, tune, and integrate -- and for all practical purposes, the final output is truly, digitally fused, at the data level. The real power to the industry and discipline is going to be when different sensor technologies are made available as modular, utility services that the consumer / customer / user can integrate via an OEM regulated set of development tools and interfaces.

IR-V
 
For us dummies, is there a chart or charts that show thermal performance relative to key dimension(factors) such as temperature, humidity, wind (which have been mentioned)? If not, I would certainly find such (a) chart(s) useful !! I'd like to have a clue as to what challenge I'm facing when heading out on a night like tonight when it is 50 degrees cooler than it was 3 days ago and raining intermitantly for past 24 hours.
 
So what objectives must be met in order to perform a sniper shot?
 
For us dummies, is there a chart or charts that show thermal performance relative to key dimension(factors) such as temperature, humidity, wind (which have been mentioned)? If not, I would certainly find such (a) chart(s) useful !! I'd like to have a clue as to what challenge I'm facing when heading out on a night like tonight when it is 50 degrees cooler than it was 3 days ago and raining intermitantly for past 24 hours.


Here is a generalized diurnal thermal emissivity chart, but you are going to have to get out there and experience it for yourself so you can learn it yourself:


Thermal%20Diuranal%20Cycle.jpg
 
For us dummies, is there a chart or charts that show thermal performance relative to key dimension(factors) such as temperature, humidity, wind (which have been mentioned)? If not, I would certainly find such (a) chart(s) useful !! I'd like to have a clue as to what challenge I'm facing when heading out on a night like tonight when it is 50 degrees cooler than it was 3 days ago and raining intermitantly for past 24 hours.

The only charts that are readily available are the ones that demonstrate the thermal radiance of different materials (i.e. vegetation, rocks, standing water, etc.) - but even those will be variable by time of year and weather conditions. Numerous academic studies in thermography show the effects of different weather and atmospheric conditions on "thermal contrast" but they represent separate bodies of research.

Short of creating a simulation routine -- which is entirely possible, just a lot of work -- the most direct method is to record thermal and corresponding "visible light" snapshots of the same outdoor view that has vegetation, rocks, standing water, etc. at regular intervals each day and night for at least a year, and to capture the time and weather metadata (e.g. temperature, wind speed and direction, barometric pressure and direction, precipitation type, Sky conditions, etc.); then to load all the images and their corresponding metadata into a database repository; and to index them so that specific snapshots or a series of them can be retrieved with the metadata -- or queried by metadata elements.

I have a series of perhaps 1,600 thermal images of exactly the same view captured from the same imager and recorded per the above, and over a couple of years in a region of the U.S. that has four distinct seasons. I've been meaning to get them all loaded into a database and metadata indexed, but the task is one of many projects I have on the back burner.

Cold ambient temperatures do not necessarily indicate a high probability of low thermal image quality. Some of the clearest, most detailed, outdoor thermal images I've taken have been in the dead of winter (Dec / Jan / Feb); at night (between the hours of 12:00 midnight and 3:00 AM); in sub-freezing temperatures (between 0 and 30 degrees F); with clear or partly cloudy skies; 35 - 45 percent relative humidity; light breeze; and following a sunny to partly sunny day.

IR-V
 
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Good info as always IR-V. Skypup, Where did you get the scale that you weighed that pig with? Your video looked good but the pic at the end did not look like a 400 lb pig.
 
Here is a generalized diurnal thermal emissivity chart, but you are going to have to get out there and experience it for yourself so you can learn it yourself:


Thermal%20Diuranal%20Cycle.jpg

I use a pair of NV/Thermal overlay goggles and am currently living in the sandbox again. The highs during the day are about 120 degrees and by the time we go out in the evenings we are in the thermal crossover range. The thermal re-calibrates constantly to put out an image but it is futile and I rarely use the thermal ability due to this. Thermal also eats batteries but that is no big deal.
 
LMAO, I'll get a couple more 400 pounders for ya to weigh on the internet scale real soon![emoji41]


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LMAO, I'll get a couple more 400 pounders for ya to weigh on the internet scale real soon![emoji41]

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I'm sure ya will!!! Lots of 400 lb, 200 yard sniper shots with a FLIR. Hopefully your next 400 lb'r is a little closer to actually being 400 lb
 
That T-75 FLIR is basically a long range sniper thermal with that 100mm lens, hogs never knew what hit them:


T-75%20SIG%20716%20Full%20Right%20Side.jpg



Four%20Flirs.jpg
 
The only charts that are readily available are the ones that demonstrate the thermal radiance of different materials (i.e. vegetation, rocks, standing water, etc.) - but even those will be variable by time of year and weather conditions. Numerous academic studies in thermography show the effects of different weather and atmospheric conditions on "thermal contrast" but they represent separate bodies of research.

Short of creating a simulation routine -- which is entirely possible, just a lot of work -- the most direct method is to record thermal and corresponding "visible light" snapshots of the same outdoor view that has vegetation, rocks, standing water, etc. at regular intervals each day and night for at least a year, and to capture the time and weather metadata (e.g. temperature, wind speed and direction, barometric pressure and direction, precipitation type, Sky conditions, etc.); then to load all the images and their corresponding metadata into a database repository; and to index them so that specific snapshots or a series of them can be retrieved with the metadata -- or queried by metadata elements.

I have a series of perhaps 1,600 thermal images of exactly the same view captured from the same imager and recorded per the above, and over a couple of years in a region of the U.S. that has four distinct seasons. I've been meaning to get them all loaded into a database and metadata indexed, but the task is one of many projects I have on the back burner.

Cold ambient temperatures do not necessarily indicate a high probability of low thermal image quality. Some of the clearest, most detailed, outdoor thermal images I've taken have been in the dead of winter (Dec / Jan / Feb); at night (between the hours of 12:00 midnight and 3:00 AM); in sub-freezing temperatures (between 0 and 30 degrees F); with clear or partly cloudy skies; 35 - 45 percent relative humidity; light breeze; and following a sunny to partly sunny day.

IR-V

I build data warehouses in my day job and would be happy to help set up a db to "index" thermal performance if that would be of any help. The concept of "index" can be expanded to any number of "dimensions" or "factors". We need at least one central "measure", as in "thermal performance" ... preferably a numerical quantity ... and then we can "index" by as many "factors" as are significant, such as temperature, humidity, wind, etc. I'd love to work on such a project. Photos could be added to the db as examples, but preferably "thermal performance" would be the primary "fact".
 
I build data warehouses in my day job and would be happy to help set up a db to "index" thermal performance if that would be of any help. The concept of "index" can be expanded to any number of "dimensions" or "factors". We need at least one central "measure", as in "thermal performance" ... preferably a numerical quantity ... and then we can "index" by as many "factors" as are significant, such as temperature, humidity, wind, etc. I'd love to work on such a project. Photos could be added to the db as examples, but preferably "thermal performance" would be the primary "fact".

Actually, the thermal images themselves can be indexed on a quantitative measure of their "thermal contrast", which is what is generally equated by a human observer as the quality of the thermal image. The engine doing this work would be an analytical tool processing the image data from the repository and then returning and inserting a value that becomes part of the metadata tagged to the image as a "record". The thermal contrast measurement would need to focus on particular zones of the image and their fractal complexity, since the attribute of thermal contrast that relates to the perception of image quality is about its utility for "identification".

I have an open account with Amazon for their integrated cloud services for big data storage and analytics, app dev, and workflow management. There's even the services to support Hadoop processing if I really want to go ape on the depth and complexity of the analytics. It is IaaS, SaaS, and PaaS at my fingertips - I just need the time to exploit it all.

I'm on travel right now. When I have a moment, I'll proxy back to home base and post some sequential, thermal images and narratives of the environmental conditions.

IR-V
 
It also helps to absorb shock and jolts while bouncing around in the trucks, UTVs, ATV, and getting in and out of tree stands too.