[Radiance-general] Radiance's conventions on locational information

[Randolph M. Fritz]

I believe this is correct, yes.

-- 
Randolph



On 2011-08-11 09:14:49 -0700, Ji Zhang said:

> Dear Radiance experts,
> 
> May I confirm with you that in Radiance there're several conventions 
> regarding some of the locational information should be specified:
> 
> 1. Longitude east of Greenwich is specified as NEGATIVE value: e.g 
> Singapore's longtitude of 104E should be specified as -104.
> 2. A positive azimuth angle denotes an angle starting from due SOUTH 
> and rotating clockwise.
> 3. Standard meridian of a city equals to the Greenwich Mean Time of the 
> city multiplied by 15, and a NEGATIVE value indicates a timezone EAST 
> of Greenwich (e.g. Singapore belongs to the EAST8 timezone, so it's 
> meridian is -120=(8*15)*(-1) )
> 
> Take London as an example, to know the solar altitude and azimuth at 
> 9:00am 1st Jan at London (altitude 51.15N and longitude 0.18W), the 
> gensky command is: "gensky 1 1 9:00GMT -a 51.15 -o 0.18 -m 0" or 
> "gensky 1 1 9:00 -a 51.15 -o 0.18 -m 0"
> 
> and you'll get:
> 
> # gensky 1 1 9:00GMT -a 51.1500015259 -o 0.180000007153 -m 0
> # Local solar time: 8.93
> # Solar altitude and azimuth: 5.5 -41.8
> # Ground ambient level: 6.0
> ......
> 
> and in this case the solar azimuth thus obtained indicates an angle 
> starting from due South and rotating clockwise for 41.8 degree. 
> 
> Thanks!
> 
> Ji
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