[Radiance-general] sun positions as calculated by gensky

[John Mardaljevic]

Lars,

 From the gensky manpage:
-m mer The site standard meridian is mer degrees west of Greenwich.  
(Use negative angle for east.) This is used in the calculation of  
solar time. Be sure to give the correct longitude also! If a time zone  
or solar time is given directly, then this option has no effect.
So it looks like solar time is not determined when you specify a time  
zone, e.g. GMT.  I never use the time zone settings myself, preferring  
to use the site meridian.  For your example:
gensky 6 21 13:30 +s -a 1.25 -o -103.75 -m -120
giving:
# Solar altitude and azimuth: 67.1 166.0
Which is much closer to where the Navy would have the sun (probably  
very nearly identical with the difference due to rounding).
-John
-----------------------------------------------
Dr. John Mardaljevic
Senior Research Fellow
Institute of Energy and Sustainable Development
De Montfort University
The Gateway
Leicester
LE1 9BH, UK
+44 (0) 116 257 7972
+44 (0) 116 257 7981 (fax)

jm at dmu.ac.uk
http://www.iesd.dmu.ac.uk/~jm