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custom-scripts

A repository of custom scripts that can be used with Sentinel-Hub services.

Normalized difference vegetation index with uncertainty

Show script or download it.

Evaluate and visualize

Basic information

General description

This script allows you to visually interpret how the normalized density vegetation index (NDVI) [1] is affected by the uncertainties in detector reflectances of the L1C products.

Since NDVI is defined as a ratio of difference over sum of bands 8 and 4 (near infrared and red):

the uncertainty propagation [3] gives us the uncertainty of the index itself as

.

where $\Delta_{B4}$ and $\Delta_{B8}$ are uncertainties of red and near infrared bands respectively (reported by ESA to be 0.02 and 0.03). We left out the mixed part $\Delta_{B4B8}$ as if the two uncertainties were not correlated.

The script encodes the uncertainty with darkness, as can be seen in following figure [2]
Color map of the NDVI uncertainty script from [2][1]

References

[1] Wikipedia, Normalized Difference Vegetation Index . Accessed on October 4th 2017.
[2] Sentinel-Hub, Ad hoc testing of algorithms globally. Accessed October 10th 2017.
[3] Wikipedia, Propagation of uncertainty. Accessed October 10th 2017.