How to get 'xap' value?

[Nutty]

Hello everyone,

I would like to thank Robin for his codes, they helped me a lot!

I would like to know how to get the 'xap' value, as I only have images of measured reflectance to do the atmospheric correction. Is there any formula to calculate it? Thanks!

I have seen an issue talk about it but to no avail. 

Looking forward to hearing back from you!

Yours,

Nutty

[Robin Wilson]

Hi,

Where did you read about the xap value and what formula do you need it for? I can’t find a reference to it in the Py6S documentation or the underlying 6S model documentation.

Best regards,

Robin

--
You received this message because you are subscribed to the Google Groups "Py6S" group.
To unsubscribe from this group and stop receiving emails from it, send an email to py6s+uns...@googlegroups.com.
To view this discussion on the web, visit https://groups.google.com/d/msgid/py6s/8c7e5072-689e-4e3f-9039-fb6dc01d13f4n%40googlegroups.com.

[Nutty]

Hi Robin,

Thank you for your response and for your patience in helping me find the necessary proof.

I came across the value xap when using sixs.exe (version 2.1) for the 6s atmospheric correction.

In the last part of the output, there are coefficients for xa, xb, and xc as well as xap, xb, and xc shown like this:

************************************************************************

        coefficients xa xb xc                 :     0.001   0.002   0.003
            y=xa*(measured radiance)-xb;  acr=y/(1.+xc*y)
       coefficients xap xb xc                :     0.012   0.0019   0.0028
            y=xap*(measured reflectance)-xb;  acr=y/(1.+xc*y)

************************************************************************

Please note that the coefficients I provided are fake and for illustrative purposes only.

And the issue mentioned about the xap is here:

        https://github.com/robintw/Py6S/pull/37

After reading through their discussion, I was wondering if there is a formula available to calculate the xap value.

And it is surprising that there are no references available regarding the xap value.

Best regards,

Nutty