Tex recently posted a question regarding Thermal Imaging (TI). He asked if the use of a thermal monocular would have been appropriate for the situation described in Chapter 6 of “The Patrol”.
Good point. It might have. The effectiveness of TI depends on a few variables but it is not the all-seeing Eye-of-Mordor most folks think it is. The proper use of cover/concealment will usually degrade the effectiveness of TI. Put something substantial between you and it and you should be good to go.
TI is greatly affected by the ambient temperature (emitted infrared radiation level) of the mass surrounding the object being targeted. On a hot, sunny day when the surrounding mass has absorbed and is now emitting a lot of that heat, TI is nearly useless, unless your body and gear is quite a bit cooler. In which case you then appear as a human-shaped, dark object. Unless you are using cover properly. For example, if I were in the prone behind a log that completely masks my body from your view, with the exception of that tiny space just large enough for me to surveil my sector, which you are currently standing in, then, depending on the range separating us, you might see that tiny dark spot (or light spot) that is the exposed portion of my face. But most likely not. We have used them pretty extensively during the day and have found ourselves chasing after small forest critters and birds perched on low limbs. More often than not, the tree trunks and limbs in our thickly forested AO create so much vertical heat clutter that we are better off relying on our normal vision.
The same concept applies when dealing with the aerial TI threat. If you are in a heavily forested area and have thick overhead concealment, than the aerial TI threat is also degraded. Max Velocity uses the TI defeating angle of concealment in the construction of his “Thermal Shield”.
Other environmental factors that can degrade its effectiveness include: Rain, fog, snow, sleet, dust and smoke.
Also, thermal imagers are completely useless when looking at glass such as a windshield or window. The glass will reflect the emitted IR image of the person using the device.
We have also tested our imagers through open doors and windows of various building in order to determine if a building is occupied. Again, everything hinges on the amount of heat that has been absorbed by the interior of the building and the use of concealment by the person occupying the building.
A word to the wise: Unless concealment is very thick, moving targets are easily tracked by TI, day or night.
So, in answer to your question Tex, yes, a TI might have been effectively used in the story against the bad guys laying in the shadows if they weren’t using cover and/or concealment properly. Especially since this portion of the story takes place on a cold day. However, was the falling sleet thick enough to interfere with the imager? Dunno, have to wait until next winter to test it.
P.S. Thermal Imagers are like ‘scopes: not all are created equal. Do your due-diligence and op for the highest resolution screen you can afford. If the options include display in both gray-scale and color, that’s a plus.