Fire events detected by the MODIS contextual algorithm are considered true fires, since the MODIS contextual algorithm has been validated systematically and offers a significantly lower false alarm rate.
Comparative analysis is conducted between earlier and later observations of fire events which are undetectable using the MODIS contextual algorithm but detectable using the improved algorithm.
If a previously undetected fire event is subsequently detected using the MODIS contextual algorithm, and/or the improved algorithm, and the event is accompanied by obvious smoke plumes, this fire event is believed to be a true fire event which was previously omitted by the MODIS contextual algorithm.
Fire events, which are only detectable using the improved algorithm at earlier time, but not detectable by both algorithms in subsequent observations, are considered uncertain spots.
Uncertain spots are further inspected using MODIS 250 m true color images. In all cases investigated MODIS 250 m true color images of the corresponding regions showed that the uncertain spots were accompanied by obvious smoke plumes. This supports the supposition that they are indeed fire spots.