[Radiance-general] [help] error message from running gencumulativesky

[Thomas Bleicher]

On Sat, Jul 23, 2011 at 8:03 AM, Ji Zhang <hope.zh at gmail.com> wrote:

> Dear Radiance experts,
>
> I got a long list of error message in the terminal when running
> gencumulativesky.exe in Win7
>
> Error!  Solar altitude < 6 degrees and Idh > 10 W/m^2 on day 1!  Attempting
> to continue!
> [...]
>


> May I ask:
> 1. Am I running the GenCumulativeSky.exe correctly?
>

If those are the only errors I expect that you do.


> 2. What does the error message mean? and Why is the error generated?
>

I haven't used GenCumulativeSky but from what I remember from the discussion
of this tool GenCumulativeSky uses gendaylit to create sky models. Gendaylit
has difficulties with low sky angles and doesn't create useful sky
descriptions for these times of day. There is only one or two errors per day
so I assume the errors happen for early morning or late evening (altitude <
6 degree). To solve this error properly we need a better gendaylit program.



> 3. Will the error affect the two files generated?
>

I would expect that these entries in your climate file are simply not
represented in the the cumulative sky model. A way to work around this might
be to hack gencumulativesky to provide gendaylit with explicit sun positions
and artificially increase the altitude to be above 6 degree.

Regards,
Thomas
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