[GRASS-user] How to deal with the warning concerning Esun during i.landsat.toar job?

[Kozlova Maria]

Dear colleagues,

I'm working with Grass Gis 6.4.4. and  7.0 (GUI interface).  I calculate TOA-reflectance with i.landsat.toar module. But some time I launch the module, the following warning appear.

WARNING! ESUN EVALUATED FROM REFLECTANCE MAXIMUM BAND

Some of my colleagues are sure that I shouldn't pay any attention to this warning as the output TOA-reflectance data is always the same with the data obtained by entering ESUN value for many routine kinds of work. Although they are not sure that it is acceptable for any special image processing, such as DOS atmospheric correction etc. And the problem is that my research concerned with many experiments of various image processing to get acceptable results.

And so I need reliable TOA reflectance data.

My question are:

1. Can anyone tell if I can get appropriate TOA-reflectance data without entering Esun value? Can this parameter significantly influence the output data? In what cases?

2. How can I enter Esun value in i.landsat.toar module?

3. Why the warning appear not every time but after the same actions and it depend on certain image (problem occur mostly with Landsat OLI images)? 


-- 
Best regards,

Maria V. Kozlova

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