While both use a type of infrared, the underlying technology is quite different. Night vision enhances existing light, but there has to be something for it to work with. Because it intensifies all the available light, night vision goggles can’t be used in daylight. In thermal monoculars, the infrared detect;radiant heat — from bodies, warm vehicles, buildings, and so forth. As discussed above, they work in absolute darkness, but they also work perfectly well in daylight. In general, thermal monoculars also have a considerably greater range.