About SkyDome Visualization

Hello forum,

When I work with Skydome component I can't but notice the irregularities in the patches, especially when using Reinhart model. For example (image), in the middle of sunny July there are suddenly some blue patches (low solar radiation). I understand it as the day being cloudy or rainy (for several days even), since single patch displays a a number of days, there are sometimes, occasionally, cloudy days that just happen to appear on one patch, thus such irregularity.

Since data is collected throughout the decades on a physical equipment, there is no way sky dome can show sunny days during the whole year (unless it is in Sahara or somewhere)

These are, of course, just guesses, I would like to hear some knowledgeable opinion on topic to be super sure.

Thanks

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Replies to This Discussion

Permalink Reply by Chris Mackey on November 20, 2015 at 10:39am

Tim,

What you are running up against here is the resolution of sky patches for the Reinhart sky being finer than the hourly resolution of sun positions. You can find a full account of this type of issue on this discussion:

http://www.grasshopper3d.com/group/ladybug/forum/topics/cumulatives...

-Chris

Permalink Reply by Mostapha Sadeghipour Roudsari on November 20, 2015 at 5:08pm

One minor comment. The sky is cumulative that can be confusing. If you want to study a single day then you should generate the sky only for the day that you're interested. Have you tried to use selectSkyMtx to generate the sky for a single day?

Permalink Reply by Tim on November 23, 2015 at 5:34am

Hi Mostapha,

Yes, I always use selectSkyMtx, just don't set the time boundaries. I've set them just to check and got results that are even more confusing. Now direct solar radiation doesn't show any value and legend values are too small.

Attachments:

CHN_Shanghai.Shanghai.583620_CSWD.epw, 1.7 MB

Permalink Reply by Mostapha Sadeghipour Roudsari on November 23, 2015 at 7:34pm

Hi Tim,

Back to values when you use only an hour the values are going to be much smaller because that's only the value for a single hour. The one that you're showing up there is a cloudy hour and sky is pretty diffuse.

I made a gif file that I hope for better understanding of the cumulative sky. I generated the sky for 20 July in Chicago between 7 am and 5 pm. On the left you see the sky for each hour and you can see how the radiation values of the sky are assigned to sky patches for each hour. On the right you can see how cumulative sky gets built based on values for each hour for a single day.

Permalink Reply by Mostapha Sadeghipour Roudsari on November 23, 2015 at 7:34pm

click on the image to see the animation

Permalink Reply by Tim on November 23, 2015 at 4:41am

Hi Chris,

Thanks for the reply and sorry for delay, time zone and work here. Anyway, I'm having a cognitive dissonance here, just to check if I understand the Reinhart patching correctly, let's say we have 8760 hours a year (which is a close approximation of a value they have in .epw file) and a dome made of 580 patches, so I thought that each patch will have 8760/580 hours, which is about 15 hours, which doesn't make sense after you say that "Reinhart sky being finer than the hourly resolution of sun positions". I don't get it man.

Permalink Reply by Tim on November 23, 2015 at 5:38am

Ok, I've reread the discussion and think I see the source of confusion, I'm starting to talk about days in the patch, where there are hours, and then you are trying to mean that but typing hours instead of days, should be "Reinhart sky being finer than the DAILY resolution of sun positions". Once again, do I understand you correctly?

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