This video is shot through a law enforcement officer’s point of view. It represents the aftermath of a foot chase where the fleeing suspect would have thrown away evidence in hopes of not being caught with it on his person. The suspect is in custody and we must now search the area where the object was tossed in an effort to recover it for evidence.
In the first part of the video, we show the officer using a time-honored tool found on every peace officer’s duty belt: the flashlight. Most of the time, individual patrol officers are not going to have access to night vision equipment, so they have to make do. During the flashlight sweep, we can see a ton of detail. As the officer walks along the brush line, he sweeps the light over the foliage. But at this distance, the light splash is almost too bright against the leaves, causing a whiteout. This hinders the officer’s ability to see detail and the outer spill of the light beam must be used. In fact, the light almost shows too much detail, effectively camouflaging the object in question. If we were to extrapolate this scenario into a full-on search, it could easily be surmised that the officer(s) would be out there all night, searching a long stretch of brush to find whatever was discarded by the suspect.
The next part of the video shows the same scenario through a night vision monocular. In this case, the night vision helps the officer see a larger area lit up. But, the dense foliage still provides a challenge to the officer trying to find the discarded evidence. As mentioned earlier, the same camouflage that works during the day is going to be just as effective at night. Another issue we see is the focal length. Night vision devices focus on a fixed focal plane and must be manually adjusted to refocus up close.
Users want to generally achieve a baseline focus where objects will be nice and crisp from about 10 yards out to infinity. But, night vision will not automatically refocus when trying to observe things up close and must be done manually. This can be challenging during a search like this where the focal plane constantly changes. A long sweep of the area yields little result and can be especially difficult it the officer is unsure of exactly what he is looking for.
The final section of the video shows the search while using a thermal device. The first thing you will notice is that the detail seems to be way less than the night vision and flashlight segments. This is because thermal will generally have a harder time differentiating between cooler objects. You can also see that the undulation in terrain as the officer walks up to the brush line, is more difficult to ascertain and can make land navigation more difficult when using a thermal device. But in terms of accomplishing the mission (finding the discarded evidence), the thermal device seems to win the night. As the officer walks up to the brush line, the heat signature of the discarded item is almost immediately visible through the dense foliage. The heat from the suspect’s body was transferred to the object and it is still warm enough to be visible to the thermal device after 15 minutes. The discarded evidence turns out to be a pistol. On a side note: thermal, like night vision, must be manually focused for up close detail during observation. While the point of this particular exercise was to find the evidence, you will notice that there is a distinct lack of detail up close when the gun was recovered because the thermal device was not refocused during the pick-up.
In the first scenario, thermal is the clear choice due to its awesome detection capability when compared to the other viewing methods.