NDMI: B08 or B8A...that is the question

I have to extract with Python the statistical value of the NDMI for small areas (tree crowns).

In all the literature (even Sentinel-Hub scripts) I have seen that the B08 band is used. In particular with the formula (B08 - B11)/(B08 + B11).

However, I noticed that EO-Browser uses the B8A band instead of the B08.

Why this difference? What band should I use to get acceptable results?

Sorry for the question (unfortunately I’m a beginner in satellite data extraction), and thank you very much in advance to anyone who wants to clarify the doubt.




Thanks for the question, yes, I can see why this maybe confusing initially to a beginner in remote sensing. The simple answer is that there is not a right or wrong answer in regards to this. Both Band 8 and Band 8A measure similar wavelengths, as shown in the table below. You will get very similar results, irrespective of which band you use as both are measuring in the NIR part of the spectrum.

Name Description Resolution
B08 NIR, 832.8 nm (S2A), 833.0 nm (S2B) 10m
B8A Narrow NIR, 864.7 nm (S2A), 864.0 nm (S2B) 20m

If you’re measuring your small areas then I would use B08 as its spatial resolution is 10m but it is personal preference. I would recommend reading deeper into the literature about this; also outside our documentation to fully understand the significance of different sensors, bands and wavelengths.

Hi William,
thank you very much.

You are always very kind.