Satellite active-fire products come from midwave infrared radiometers on polar-orbiting satellites: MODIS on Terra and Aqua at 1 kilometre resolution, and VIIRS on Suomi-NPP and NOAA-20 with a 375-metre imagery band. A detection algorithm compares each pixel's midwave brightness against its neighbours and flags anomalously hot ones. Two facts govern everything you do with the output. A detection is a pixel centroid with a confidence value, not a fire boundary, so plotting it as a dot on a map is correct and plotting it as a fire outline is not. And detection is driven by the fraction of the pixel that is burning and how hot it is, not by area alone: because emitted radiance rises steeply with temperature, a very hot flaming front a few metres across can be detected in a 375-metre pixel, while a cool, smouldering fire covering far more ground can be missed entirely. Add that each satellite passes a given place only a couple of times a day, and off-nadir pixels are much larger than the nominal size, and the picture is complete. After this Concept you can read a satellite fire detection as a hot pixel with a time and a size, and say what it does not tell you.
The VIIRS active fire detection product is a satellite remote-sensing data product that uses a hybrid contextual algorithm operating on mid- and long-wave infrared wavelengths to identify fire pixel …