FORMA Alerts (WRI/GFW/FORMA/alerts)

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.

The percentage of clearing takes a value of 0, no clearing detected,
or in the range [ecogroup_bound:100), where ecogroup_bound is given by
WRI/GFW/FORMA/thresholds .
The time periods over which data is collected varies by N-days, where N is the number
of days between the alert_date and the last MODIS NDVI update.