Mapping a specific emittance line for gases at surface

Hi there,

I’m very new to SNAP so apologies if this is basic. I am trying to show a specific nm on the map minus the rest of the spectrum and bands. This would be at BOA. I have attempted spectral unmixing but got stuck. Are there any guides out there which I could use?


I’m not sure if I understand you correct.
You want to see the values at a certain wavelength?
SNAP can only show the values which the sensor has measured.
For Sentinel-2 the measured wavelengths are
442.7, 492.4, 559.8, 664.6, 704.1, 740.5, 782.8, 832.8, 864.7 , 945.1 , 1373.5 , 1613.7 ,2202.4
To get BOA values you need to use the level 2A data of Sentinel-2
SNAP shows the values of those wavelength bands in the Pixel Info View.

But you can also use the the Spectrum View (in the Optical menu).

Here all measured wavelengths are shown in a graph when you move the mouse over the image.

Thanks Marco - that’s really helpful.

If I want to find areas where a specific wavelength is found, that is not one of those you specified above, is it impossible to see it? Or do I look for the wavelength closest?

For example, I would like to see where methane pollution is located in the BOA near cattle ranches. Is this possible?

Again, I apologise if these are stupid questions.

I had a quick look at this document: Airborne measurements of atmospheric methane
column abundance…

As methane is absorbing in a narrow bandwidth at ~1650nm, this is covered by the 1613 channel.
In the document some other sensors are mentioned. It has a bandwidth of 86 nm. So the methane wavelength is included and the channel should be affected.
If this is enough to detect methane clouds, I don’t know. Probably some specific sensor is more appropriate. Specifically intended for the methane observation is Sentinel-5p.
ESA - New Space satellite pinpoints industrial methane emissions
The data can be opened in SNAP but it is not specifically supported.
Better you have a look at the Atmospheric Toolbox