[GRASS-user] How to determine Grass (i.atcorr) tool control file's “visibility for the aerosol model [km]” parameter value

[iat bd]

Dear All,

In Grass, the Atmospheric Correction tool (i.atcorr) reference do not
provide information with regards to the parameter "visibility for the
aerosol model [km]" in the control file. I have searched exhaustively
online. But could not find the data source or methodology to generate it.
Does it mean Vertical visibility? As far I can understand, the parameter
should be independent of the visibility map (because visibility map raster
cell value reflects count # of other cells it can see).

I have already explored the Aeronet website but could not find any
Visibility (km) data. I am familiar with the alternate method (Setting
visibility equal to zero and providing ADO at 550 nm) but I would like to
explore the other method using DEM, visibility map and visibility for the
aerosol model [km] parameters.

Please let us know the data source (if there is any) and calculation
methodology for "visibility for the aerosol model [km]" preferably, in
layman's term.

Kind regards,

Imtiaz
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