What is Surface Reflectance?

Surface reflectance represents the proportion of light that is reflected by the Earth's surface. It is calculated as the ratio of surface radiance (the light reflected by the Earth) to surface irradiance (the light that reaches the Earth's surface), and it is a dimensionless value typically ranging from 0 to 1. The Surface Reflectance (SR) Product is generated from the standard Planet Analytic (Radiance) Product. This process involves converting the data to top-of-atmosphere reflectance and then applying atmospheric corrections to derive the surface reflectance (which pertains to the bottom of the atmosphere).

For the PlanetScope Dove constellation, Planet employs the 6S (Second Simulation of a Satellite Signal in the Solar Spectrum) atmospheric radiative transfer model, complemented by ancillary data from NASA's MODIS (Moderate Resolution Imaging Spectroradiometer), to accurately account for atmospheric influences on the signal detected by the sensor.

For those interested in learning more about the 6S model, there is a Python interface Py6S, whose documentation provides in-depth information and guides on how to use Py6S for running 6S simulations​​.

See our white paper on Planet Surface Reflectance Products.

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