[Radiance-general] DAYSIM vs. Radiance illuminance values

[Reinhart, Christoph]

Dear Nicolas:

 

I agree with Jan that using gensky and comparing the results with Daysim
is a bit meaningless. As far as accurate Daysim accuracy compared to
Radiance classic is concerned, we had an email trail on this  last week
in the Daysim discussion forum
(http://groups.google.com/group/daysim/browse_thread/thread/3029e67b22c2
2a830) . 

 

Best regards,

 

Christoph

 

From: radiance-general-bounces at radiance-online.org
[mailto:radiance-general-bounces at radiance-online.org] On Behalf Of
Nicolas Roy
Sent: Monday, September 22, 2008 10:04 AM
To: Radiance general discussion
Subject: [Radiance-general] DAYSIM vs. Radiance illuminance values

 


Hi, 

I'm making a short comparison between illuminance values obtained in
DAYSIM and Radiance for a specific day/time, and the results I obtain
show a  ratherbig difference with Radiance having values twice as high. 

I compare the values in the annual illuminance profil (.ill) generated
by DAYSIM, with values I obtained in Radiance for the same day/time. I
defined the Radiance sky description using the "direct normal
irradiance" and the "diffuse horizontal irradiance" values from the
climate data used in DAYSIM. 

What can be the source of such large differences? 


I use the following in Radiance: 

##sky 

gensky 6 21 12.5 -a 52.47 -o -15.4 -m -15 -r 35 -B 363 > sky001.rad 


##out.rad 

skyfunc glow sky_glow 
0 
0 
4                0.9                0.9               1.15
0 

sky_glow source sky 
0 
0 
4                  0                  0                  1
180 

#a green ground 
skyfunc glow ground_glow 
0 
0 
4                0.2                        0.2               0.2
0 

ground_glow source ground 
0 
0 
4                  0                  0                 -1
180 

##rtrace rcalc run 

oconv sky001.rad out.rad material.rad geometry.rad > 001.oct 
rtrace -w -h -I+ @options.opt 001.oct < sensors.inp | rcalc -e
'$1=($1*0.265+$2*0.670+$3*0.065)*179' > 001.ill



-Nicolas 

nicolas.roy at velux.com 






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