Table 1. Environmental indicators calculated from the 4-bands SPOT-5 image at 2.5 m spatial resolution and potentially associated with the presence of water or the presence of An.gambiae s.l.

Environmental indicator	Spectral bands combination*	Description	Ref.
NDVI (Normalized Difference Vegetation Index)		A value superior to 0.2 usually corresponds to a vegetated area, which gets denser when this value rises. Negative values indicate non-vegetated features such as barren surfaces (rocks and soils), water, built-up areas or asphalt.	62, 63
NDWI Mac Feeters (Normalized Difference Water Index)		It delineates open water features while eliminating the presence of soil and terrestrial vegetation features. Its value increases with the presence of water and decreases with the presence of vegetation. It is also suggested that it may provide turbidity estimations of water bodies.	64
MNDWI (Modified NDWI Mac Feeters Index)		It can enhance open water features detection while efficiently suppressing and even removing built-up land noise as well as vegetation and soil noise.	65
BI (Brightness Index)		It characterizes soil physical properties, roughness, compactness or moisture content. High values correspond to natural or anthropogenic bared soils, without vegetation.	66

^*NIR : Near infrared, SWIR : Short wave infrared.