<div dir="ltr"><span style="color:rgb(34,34,34);font-family:"Helvetica Neue",Helvetica,Arial,sans-serif;font-size:15px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:19.5px;text-align:left;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;display:inline!important;float:none;background-color:rgba(248,248,248,0.6)">Dear All,<br></span><div><span style="color:rgb(34,34,34);font-family:"Helvetica Neue",Helvetica,Arial,sans-serif;font-size:15px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:19.5px;text-align:left;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;display:inline!important;float:none;background-color:rgba(248,248,248,0.6)"><br>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). <br><br>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 </span><span style="color:rgb(34,34,34);font-family:"Helvetica Neue",Helvetica,Arial,sans-serif;font-size:15px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:19.5px;text-align:left;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;display:inline!important;float:none;background-color:rgba(248,248,248,0.6)"><span style="color:rgb(34,34,34);font-family:"Helvetica Neue",Helvetica,Arial,sans-serif;font-size:15px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:19.5px;text-align:left;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;display:inline!important;float:none;background-color:rgba(248,248,248,0.6)">visibility for the aerosol model [km]</span> parameters. <br><br>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.<br><br></span></div><div><span style="color:rgb(34,34,34);font-family:"Helvetica Neue",Helvetica,Arial,sans-serif;font-size:15px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:19.5px;text-align:left;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;display:inline!important;float:none;background-color:rgba(248,248,248,0.6)">Kind regards,<br><br></span></div><div><span style="color:rgb(34,34,34);font-family:"Helvetica Neue",Helvetica,Arial,sans-serif;font-size:15px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:19.5px;text-align:left;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;display:inline!important;float:none;background-color:rgba(248,248,248,0.6)">Imtiaz<br></span></div></div>