Raw earth imagery from satellites is blue-ish due to atmospheric scattering. Above you can see the before-and-after comparison. On the left the blueish “top of atmosphere” reflectance, on the right the calculated “surface reflectance”. As I mentioned yesterday, we use LEDAPS, a NASA developed code, to remove this effect.

This correction is an important step in our processing pipeline not only to make beautiful maps truer to what one would see from ground, but also key for measuring vegetation indices, albedo, burned area, land cover type or temporal change.

Thanks @andershovmoller for the motivation to do a side by side picture!