aerosol optical depth demystified

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@46313 15284696-431f-4ddb-bdfa-cd5b030d7da7

imagery/i.atcorr/i.atcorr.html

@@ -342,14 +342,19 @@ refractive index.</td>
 
 <h3>D. Aerosol concentration model (visibility)</h3>
 
-<blockquote>If you have an estimate of the meteorological parameter visibility
+If you have an estimate of the meteorological parameter visibility
 v, enter directly the value of v [km] (the aerosol optical depth (AOD) will be
 computed from a standard aerosol profile).
-<p>If you have an estimate of aerosol optical depth, enter v=0 for the
-visibility and comma-separated enter the aerosol optical depth at 550nm
+<p>If you have an estimate of aerosol optical depth, enter 0 for the
+visibility and in a following line enter the aerosol optical depth at 550nm
 (iaer means 'i' for input and 'aer' for aerosol), for example:<br>
-v=0, 0.112
-<p>NOTE: if iaer=0, enter v=-1.</blockquote>
+<div class="code"><pre>
+0                            - visibility
+0.112                        - aerosol optical depth 550 nm
+</pre></div>
+
+<p>
+NOTE: if iaer is 0, enter -1 for visibility.
 
 <h3>E. Target altitude (xps), sensor platform (xpp)</h3>