actual radiance value

radiance-general
1

Hello experts:

Is the following understanding of "radiance" in the Radiance program
correct?

If I input irradiance (W/m2) values in Gendaylit, the inputted irrdadiance
values will be converted to zenith luminance (cd/m2) according to Perez's
model (1990), then luminance will be converted to "radiance" (W/m2*sr) value
in the visible range by dividing 179 (I did not see "179" in the
gendaylit.c).

So, the irradiance value calculated by the Radiance program should be
different from irradiance value in weather file even though the actual
irradiance values in the weather file are used as an input of
gendaylit (assuming Perez's model is perfect). But the illuminance /
luminance values calculated by Radiance should be accurate in theory (also
assuming Perez's model is accurate).

PS, my school library does not have permission to access the full text of
the Perez's paper (1993) referred to by Gendaylit program (url:
http://www.sciencedirect.com/science/article/pii/0038092X9390017I). If
allowable, could someone send me this paper?

Thank you,

Jia

2

Sorry to interrupt you, I can access the paper now. Thanks.

ยทยทยท

On Sat, Jul 16, 2011 at 12:16 AM, Jia Hu <[email protected]> wrote:

Hello experts:

Is the following understanding of "radiance" in the Radiance program
correct?

If I input irradiance (W/m2) values in Gendaylit, the inputted irrdadiance
values will be converted to zenith luminance (cd/m2) according to Perez's
model (1990), then luminance will be converted to "radiance" (W/m2*sr) value
in the visible range by dividing 179 (I did not see "179" in the
gendaylit.c).

So, the irradiance value calculated by the Radiance program should be
different from irradiance value in weather file even though the actual
irradiance values in the weather file are used as an input of
gendaylit (assuming Perez's model is perfect). But the illuminance /
luminance values calculated by Radiance should be accurate in theory (also
assuming Perez's model is accurate).

PS, my school library does not have permission to access the full text of
the Perez's paper (1993) referred to by Gendaylit program (url:
http://www.sciencedirect.com/science/article/pii/0038092X9390017I). If
allowable, could someone send me this paper?

Thank you,

Jia