Background Characterisation

The Background Characterisation step provides an estimate of the radiometric signal of the potential fire pixel in the absence of fire, based on statistics derived from background pixels located in a window immediately surrounding the potential fire pixel. These background estimates are also used to determine whether the observed potential fire pixel signal is sufficiently different that it can be confirmed as a fire pixel.

The background window extends from a small exclusion zone immediately surrounding the potential fire pixel out to a variable upper limit. This limit is increased until sufficient valid background pixels have been identified, or until a maximum size has been reached. Pixels are considered valid if they are cloud-free land pixels that for daytime observations are not influenced by strong sun glint and which, so far as possible, do not contain fires. If insufficient pixels have been identified at the maximum window size, then the characterisation is unsuccessful.