DN. dl, Reflectance

[AstraVic]

I read a lot of similar topic on Step forum about reflectance, Dl, DN and radiance.
But I am probably confused, and I have some questions. Please, help.

The first question is:
Is it possible to create a pic like this (in % or in range from 0 to 1) ?

2. Why reflectances don’t have a unit?
   Marco Peters wrote

@marpet

But reflectances don’t have a unit. It is the ratio of reflected light by the surface.
You can say that the unit is % or dl (dimensionless).
You can see the unit when you select the band and choose from the toolbar.

So , when I create spectral view in Optical tools, I see dl or %? What kind of Sen2 product should I use? Because and L1C and L2A give similar result ,

even when I divided by a thousand.

3.Why in tool “Spectral Unmixing” only a radiance is available?
4. What is difference in radiance and reflectance? And dl and DN?
5. What scientific books or papers do you recommend to read read? The main thing that it was written in simple language

[falahfakhri]

@AstraVic

Is it possible to create a pic like this (in % or in range from 0 to 1) ?

Yes, it is possible to create signature diagram using SNAP, for selected features, for instance vegetation, urban area, water, soil, et. al.

Please have a look at this video,

Exploring spectral response curves from Sentinel-2 in SNAP

@AstraVic

Why reflectances don’t have a unit?
Marco Peters wrote

Source

Have a look at this video as well explains the difference between the three component,

Digital Number, Radiance, and Reflectance

@AstraVic

So , when I create spectral view in Optical tools, I see dl or %? What kind of Sen2 product should I use? Because and L1C and L2A give similar result ,

Take a look at these threads,

TOA and BOA

sen2cor converts L1C products into L2A

Evaluation of Sentinel-2 Red-Edge Bands for Empirical Estimation of Green LAI and Chlorophyll Content

@AstraVic

What scientific books or papers do you recommend to read read? The main thing that it was written in simple language

remote sensing books pdf

INTRODUCTION TO REMOTE SENSING

The following is good book, if it is available in your library,

Remote Sensing and Image Interpretation, 7th Edition

[AstraVic]

So, TOA radiance is every light which reflects off the planet as seen from space measured in radiance units. Right?
And atmospheric correction is then a method how to try to remove influence of just that portion of light reflected off atmosphere on the image and preserve the part reflected off the surface below.
And this is the way to get BOA (bottom of atmosphere) or surface radiance, rigft?

L1C products are TOA, and when I use sen2cor, I convert TOA to L2A - BOA, is not it?

So, is it try, that in this video we can see TOA reflection graph, because the author of video used L1C product?

And can I suppose (or not), that dl is equal % (BOA) when I use L2A - BOA product, and create pics like this ?

[ABraun]

yes, for L2A products % would be more suitable in most cases.

If you want it in your graph, you can replace it in the band properties (for all bands)

[AstraVic]

OK, thank you. Everything is clear with Sentinel 2 products.

But what if we talk about Landsat? I must create derivative products by myself, using formulas in Handbooks, or I must use plugins, for example iCOR or another program for example, ENVI,isn`t it?

By the way, can you explain, please, what is dB ?

[ABraun]

You can download calibrated Landsat products in the EarthExporer. It depends on the product level what you get.

dB is related to the backscatter intensity of radar data. It is not used in the context of optical images.

[AstraVic]

@ABraun

You can download calibrated Landsat products in the EarthExporer. It depends on the product level what you get.

Ok, understand.

@ABraun

dB is related to the backscatter intensity of radar data. It is not used in the context of optical images.

Yes, I know it. I apologize for writing in the wrong section.