As some of you might be aware, ESA will be updating the Sentinel-2 processing baseline in January 2022. One breaking change is the definition of digital numbers (DN) in the source files. Negative reflectance values will be possible and DNs before and after the change are shifted and will no longer be comparable.
To keep this transition as smooth as possible, we are introducing the
harmonizeValues parameter. This optionally goes is in the
input.processing section of your request.
The default value is
true and this means that without needing to do anything, you will get data exactly as before.
harmonizeValues can be
true (default) or
false, and it’s behavior depends on the units:
harmonizeValues = true: negative reflectance values are clamped to zero. In other words, pixels with negative reflectance return zero reflectance instead.
harmonizeValues = false: negative reflectance values can be returned.
harmonizeValues = true: DN values are harmonized so they are comparable with data from previous baselines. Therefore it still holds that
DN = 10000 * REFLECTANCE. In addition, negative values are clamped to zero.
harmonizeValues = false: DN values are exactly as provided in the source files themselves. The “true” DN value, you could say. Don’t forget that values have different definitions with different processing baselines, careful with mosaicking!
So if you are happy with the way things are, there is no need to do anything. However, if you would like to benefit from negative reflectance introduced in the new procesing baseline, consider adding
harmonizeValues=false to your request.