L2A images to range 0 to 1

1

Hi everyone,
Please, someone can help me to know how to convert sentinel L2A product (BOA) to range 0 to 1?
I tried to divide all bands by 10000, but doesn’t work. Please, someone can explain how I can do this?
I can use Qgis, R, Grass, Arc, but I need to know which is the equation.
Thanks so much,
Juliana

2

Dear Juliana,

To obtain reflectance from Sentinel-2 L2A images from Sentinel Hub you can either:

  • download the data directly as reflectance as floats (not recommended unless you have a very specific reason, because it costs more processing units and the images returned are heavier).

  • request the data as “Digital Numbers” (DN) as integers and convert the DN to reflectance on your side. As you correctly noted, to obtain reflectance you need to divide the DN bands by 10000 (see here).

I tried to divide all bands by 10000, but doesn’t work.

Could you provide a little more information on what didn’t work and how you tried to convert your DN to reflectance? That way we can offer some guidance on retrieving the information you need.

Maxim

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Hi Maxim,
Thanks so much by reply.
I downloaded the images 2A on the ESA website and the jpeg is integer files. So, I multiplied the bands by 1.0. Is it right?
After, I divided the values by 10000. However, the bands have a range of more than 1. For example, reflectance for band 4 has a maximum value of 1.61. What happens?
Thanks so much,
Juliana

4

Having reflectance values larger than 1 is not uncommon. This can be due to light-scattering in clouds (additional illumination), specular effects (a glass roof reflecting light towards the satellite) or sloping bright surfaces (snow in the mountains).

If you want more details on the subject, Olivier Hagolle from CESBIO wrote a very interesting blog post here that explains it better than me. And if you want to dive deeper into the equations behind the terms used in Remote Sensing, this article is a goldmine of information.

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