FORMA alert thresholds (WRI/GFW/FORMA/thresholds)

FORMA alerts are detected using a combination of two MODIS
products: NDVI (Normalized Difference Vegetation Index) and FIRMS
(Fires Information for Resource Management System). NDVI updates are
processed every 16 days, while fire updates are processed daily. Models
are developed individually for each ecogroup to relate the two inputs to
the area of clearing, using the Hansen annual tree cover loss data to train
the model. The minimum threshold to qualify as an alert is 25% of the pixel
cleared, though thresholds vary by ecogroup to minimize false positives.
Here is an example script
for a quick introduction to the FORMA datasets.

This image contains the thresholds at which, when crossed, a FORMA alert is
produced. The values are equal to max(25,40%*RegionalMax), where RegionalMax
is the historical maximum clearing for a pixel in this ecogroup. Ecogroup
geometries can be found here.