A bigfoot is hiding in the Canadian Pine forests. Why haven't the thermal imaging satellites picked up the huge animal all this time?
Is there some way an animal can hide from thermal imaging cameras? Maybe by putting snow on themselves?
Not all warm blooded animals stand out on thermal imaging - the example that comes to mind is the Polar Bear, which is so effective at heat retention that scientists are trying to mimic it for stealth and camouflage reasons. The Canadian forests are also quite cold so it would be of little surprise to me if a bigfoot creature which inhabited such a region was also close to invisible on thermal tracking.
As for hiding from satellite tracking, this would be a lot easier than you think for several reasons; first is that just because we have complete satellite coverage across the planet doesn't mean that all that data actually gets looked at; most of it is only checked if there is a good reason to do so. It may be possible for instance that Russia may be spying on Canadian ground due to mineral resource and oil competition for instance, but even then that means looking for new humans or building operations that might be oil wells, mines, derricks and the like.
Secondly, even if the tracking satellite data is being used by scientists working on wildlife studies, something the size and thermal signature of bigfoot is probably going to be 'assumed' to be some form of bear. Bears are known to be in the forest, whereas bigfoot isn't and as such the default categorisation will be to something that is expected to be there, not put to the side as a potential spotting of something new.
Finally, there is also the fact that we're talking a forest, meaning that visuals are going to be obscured from full view most of the time, and at best even if you were evaluating satellite data to refine the location of a ground team to go in to search for bigfoot, seeing an obscure animal profile from space and then going in and trying to find that same animal on the ground for definitive proof are two very different things. Bigfoot may not know about satellites, but it will definitely know about these dangerous creatures called humans that clamber through the forest looking for them.
Above all else, never undervalue complacency as a shield; when in doubt, most people who are going to be reviewing the data are going to interpret the data in the manner most conducive to generating the least amount of possible work for them.
Spies are not going to loudly proclaim the discovery of bigfoot and have to explain what their satellites were doing there in the first place.
Prospectors are not going to loudly proclaim the discovery of bigfoot and have to justify why they should be allowed to disturb a pristine environment with hither-to unknown life forms roaming around in it.
Even climate scientists are not going to loudly proclaim the discovery of bigfoot and have to explain their interpretation to the mainstream body of scientists without any clear proof to support their statements.
This is all especially so when you think of the fact that most people will be of the opinion that if bigfoot is out there, then he would have been found by now because, let's face it, we have all this satellite tracking technology out there that would have found him by now...
So, you not only have to combat complacency, but a growing belief that 'someone else should've found him by now' that becomes stronger the longer bigfoot remains undiscovered.
I wanted to expand on some of the answers already given. I am not a biologist or zoologist and I do not use the thermal bands of satellite imagery. But I am a geographer I do use satellite imagery for change detection and NDVI. Tim B II and Keith Morrison gave good answers but I wanted to go into a little more technical aspect. It also gives me a chance to nerd out on remote sensing.
The spectral resolution is the wavelength of radiation (UV, IR, thermal, or visible light) of interest. In the case of thermal imaging of coal mine fire analysis, they used sensors with wavelengths in the bands of 10.78 – 12.27µm. That is the main Thermal radiation band that can be detected from space without interference from the atmosphere.
The spatial resolution is the area that one pixel in the image covers. While there are some sub-meter spatial resolution sensors aboard satellites most are much coarser. Even at 1 meter resolution that means that every pixel in the image represents approximately 3 feet by 3 feet. I know sasquatch is supposedly a large being but it would probably be at most 1 pixel. If it was on the line between pixels it would probably be washed out by surrounding vegetation.
Temporal resolution is how often that area on earth has images taken of it. Most satellites for imaging are zooming around the earth in an orbit going from pole to pole. That means the earth turns underneath the satellite as it cuts a diagonal swath. Because of this for a satellite to take an image of the exact same patch of earth it can take up to 16-20 days. This can be mitigated by constellations of multiple satellites or geosynchronous satellites. Geosynchronous / Geostationary stay in the same place relative to earth and therefore have fine temporal resolution but are much farther away (farther out in space) and thus have lower spatial resolution.
There is a balancing act between these 3 resolutions. When we get better resolution on one the others usually suffer. Here are some comparisons of satellites and their resolution:
LandSat 8 bands 10 and 11 are the thermal infrared at a resolution of 100m and 16 day temporal resolution.
Modis between the Terra and Aqua satellites has a temporal resolution of one to two days but the spatial resolution for bands 31 and 32 that sense surface and cloud temperatures is 1000m
SuperView-1 has a panchromatic (black and white) resolution of 0.5m, and with 4 satellites has a temporal resolution of 2 days but has no thermal sensor
GOES (Geostationary Operational Environmental Satellite system) 17 is a geosynchronous satellite that takes imagery of the continental US every 5 minutes but the spatial resolution of the thermal band(s) is 2 kilometers (1.2 miles).
So as you can see even if Bigfoot was out and about the few seconds when a satellite passed overhead on the 2nd or 16th day of repeat it would be lost in the background at most sensor’s resolution. Clouds and trees to some extent can also obscure some of the sensors.
When I do remote sensing I usually do pan sharpening, some sort of classification, and change detection. Pan sharpening is adding the panchromatic (black and white) band to the visible bands to create a higher spatial resolution image since the panchromatic band usually the highest resolution. Then I do supervised classification. I pick out some areas in the image and tell the software that they are trees or houses or roads then the software will check every pixel in the image and try to assign it to a category. It is not perfect but it works pretty well. Classification is the step where it might "find" bigfoot but it would just be one pixel in a group that the software could not place and lumped into "unclassified". Then there is change detection. I take old classified images and ask the software to compare that to new images to highlight what has changed. I am not looking at every pixel of an image or even looking at the images most of the time just what areas have changed and displaying that.
In my opinion aerial orthophotography (airplanes taking pictures) would be a better route. I know that Los Angeles County has 4 inch spatial resolution imagery flown every year. That would allow one to see such a creature but there would still be vast areas that would have some kind of methodology to look at the study area.
Simple reason: satellites don't actually work as well as they do in TV and movies. While visual imagery can be used to count individual animals, infrared has a coarser resolution and thus, at best, you might get a small blob indicating something living when it can get a glimpse through the trees.
Which causes a small issue: why would someone think the thermal blob was a sasquatch and not a grizzly, black bear, moose, cougar, or other mammal?
Bigfoot is not a mammal.
It does not show up on thermal imaging because it is cold blooded; a terrestrial amphibian. This also accounts generally for the tremendous ability of Bigfoot to hide. It can seek out bodies of water and estivate for long periods on the bottom. No-one thinks to check the river for Bigfoot.
For other non-heat related reasons, first, the Pacific North West is entirely within the boundries of the United States and Canada, who share some of the strongest relations of any nations (not to mention the longest continuous border between two nations in the world). Most sattellites that can pick up a (large) ape like mammial are not going to be thermal imaging satellites but spy satellites. And these types typically are looking in visible light spectrum rather than thermal imaging because they are looking for military activity from both the U.S. and Canada (pfft).
Well, the former of the two does the vast bulk of the heavy lifting in the alliances, but the Pacific North West doesn't have much in the way of strong activity, Califorina is much more developed than Origin (most Americans know it as the state they died of dysentery trying to reach in that video game) or Washington, though the latter has a major submarine base. California entered the Union well before they U.S. even had the other two as territory, let alone states.
Spy Satellites are looking for movements of supplies and equipment and people, and while the best are reportedly able to be able to read news paper headlines, it's usually monitoring movenment of bulkier equipment than people. Because the orbit gives it a limited window to take these pictures, they're not going to be looking at other things, but the general bases they are tasked to look at.
And of course, while they have a top down view, it's very easy to hide from them under cover. When India detonated Smiling Budda, it's first nuclear bomb, it came as a surprise to the world. India was aware of the eyes in the sky so the test sight was given covers to hide the nuclear device prior to detonation. Naturally, that cover was vaporized rather quickly after detonation, but the first warning that there has been a nuclear detonation anywhere in the world is going to come from geologists, not spy satellites (The U.S. Geological Service is the reporting agency for any nuclear detonations and in many cases, they're work is how we know there was a big boom).
I say this because the Pacific North West is technically a rain-forest and the largest one in the temperate regions of the planet to boot. The foliage is incredibly dense, and the region spans from Northern Califorinia, through Origin and Washington states, into British Columbia and southern Alaska. The terrain is fairly rugged as well and even if you were looking for Bigfoot with satellites, the foliage could be too dense to see, and a wild bipedal humanoid in brown fur will look similar to a hiker or camper in the woods and wouldn't be considered something worth looking at. If you're going heat signatures, the same thing applies. While Sasquatch is not recognized as existing, it's still hypothesized that it would be genetically close to homo sapien and reported sightings will usually start with the witness saying his/her first impression was that it was a large man. Big burly men in brown clothing in the woods is fairly typical in the region and wouldn't be an initial cause for alarm. Most times, the reported sighting is flagged only when the figure starts behaving more animal like than human like (there's a recording you can find on Youtube from a 911 call where the caller is calling the cops about an unidentified person who killed his dog while it was outside. At one point he sees the person and describes him as looking like a very big man (Figuring at least 7 feet in height) and built like an American Football player and the caller can't make out any details other than he's covered in black clothing. It's not known if this is an actual encounter, but the suspect pool of 7 foot tall beefy humans is rather limited (extremely tall people tend to be very skinny. Most competitive bodybuilders are well under 6 feet tall because even if their taller counterparts work out just as much as they do, it takes longer to get to a size that looks big in competition.).
Too many other heat sources.
Bigfoot while large, is not more massive than a mature black bear, or a moose.
The population of BF is small. At least when I've ventured into Willmore Wilderness (North of Jasper Park) I usually will see black bear, grizzly bear, and moose tracks, as well as horse tracks from hunting parties, I don't see human/ape like tracks.
So the population of BF is small compared to the population of these other critters.
The best time for detecting a thermal signature is at night, when the surface of the earth is cold compared to the surface of BF.
With people, aka the naked ape, we like to keep our skin about 8-10 C cooler than our body temperature. This allows us to dispose of surplus heat without sweating much. At lower temperatures we put on synthetic fur (clothes) to keep our heat loss at acceptable levels. Many animals go through an annual fur growth/shed cycle to do the same. They will also seek out places that reduce excessive heat loss. If you camp, you can easily test this. Spend two nights out, one night directly under the stars, and one night under any tree with a dense canopy. You will be warmer (and have less condensation on your sleeping bag) under the tree.
Now, if you have been in the rockies, you will know that they come by that name honestly, and there are many rocks. A boulder with the sun shining on it in the day will get quite warm, and will take hours after sunset to cool off. Patches of bare earth also act like this.
Bigfoot in the day time is a blob of warm barely warmer than the surrounding land.
Bigfoot in the evening is a warm blob in a bunch of other warm blobs -- stationary ones called rocks, and moving ones called moose and bear.
Bigfoot at night is either napping under a tree, or foraging much like a bear.
Bigfoot at dawn might be caught if in the open, and someone tries to correlate sub meter thermal pixels, with shadows that are the wrong shape for moose.