Sun Shadow Frequency - General questions

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04-11-2023 04:29 AM
lena_a
by
New Contributor II

Hello!
I am using ArcGIS Pro 3.1.1 and was trying to use the Sun Shadow Frequency tool. 

I had no idea what the correct parameters were, so I just chose my features and then run the simulation, set with the current time. Now I have the map with two colors, 0 and 1. Does this mean now that all areas with 1 are in the shadow and the ones with 0 are without (at least that's what makes the most sence to me)?

What I originally wanted to do is creating a layer that shows me the shadows of my buildings during a whole (summer) day. But everytime I try to run the task with setting a start and an end time, I only get a layer with only one color (and no shadows?)... 

Can someone please help me and tell me 

1. What exactly is the output of the tool?

2. what parameters do I have to put there to get a sucessful simulation?

 

Thanks alot!

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5 Replies
Remi_Foicik
New Contributor II

Hello Lena,

Sorry, I'm maybe late but I was working with this tool recently and I had the same questions, I suppose you're working on urban heat islands ? 😉

The output of this tool is a raster where the value of each cell corresponds to the number of time where the cell isn't exposed with a direct sight line to the sun (it corresponds in your case to being in the shade)

For example, I started the geoprocessing with my 3D model for a whole day of summer with a time interval of 1 hour, the day has 15 hours from the dawn to dusk so my output values i between 0 and 15 where :
0 : the cell is constantly exposed to the sun (15 hours of exposition)  (very warm red in my capture)
15 : the cell is never exposed directly to the sun (refreshingly blue in my capture)

RmiFOICIK_CAVGP_0-1686664284388.png

for example, here the variables I'm using :

RmiFOICIK_CAVGP_1-1686664589951.png
With the daylight Saving time box checked, the tool knows the time of sunshine at this date so it makes only 15 iterations despite the fact that I launched the tool from 01:00 to 23:00 for august 1st with a 1 hour interval (22 iterations).

Warning, the process could be very long depending of the number of 3D object, the cell size of output raster and the number of iterations you're asking for.

I hope It could help you

Cheers,
Rémi

 

lena_a
by
New Contributor II

Hello Rémi, 

sorry for my late reply, I didn't get any notification about your answer!

Your answer really helped me, thank you very much 🙂 I was now able to run my first simulation with a result I could use (in parts). 

I had to stop the first simulation because after 5 days I had only 1% processed, so many objects were included.. 

I have a question regarding your 3D model. Did I see it correct that you were able to include your trees in the shadow processing? If yes, could you tell me how you were able to use the trees?

Thank you again!

Best wishes, Lena

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Remi_Foicik
New Contributor II

Hi ! 

You can add multiple inputs in the geoprocessing tool as long as they're multipatch feature class. 

Remi_Foicik_0-1691398546869.png

But the more objects, the longer the calculation time....so it will be a problem for you apparently. 

I checked the tool and unfortunately, it's not very well optimized. Sun shadows frequency can't use GPU and it can only use mono-thread CPU calculation power.

What I did was segmented my input datas and I launched several instances of the tool at the same time.


For example, if you want to make a simulation for a whole day, you can launch several instances of ArcGIS Pro as your CPU and RAM allows (or by script, it was what I did) and start the geoprocessing tool with different time interval (00:00-01:00; 01:00-02:00; 02:00-03:00;....)

If you lauch the tool on a whole day of summer per hour, you can (virtually, depending of you computer) divide the time it will take by 15 😉 

After that, you can do a simple raster calculation at the end with all ouptut rasters. 

Hope it could help !

Rémi

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AndressaMuraro
New Contributor

Hello community!

I'm trying to use the tool, but the Input Features already returns an error.

AndressaMuraro_0-1702241621506.png

 

My features are polygons and I've already made sure it's a Feature Layer. I tried Polygon Z, Polygon and Polygon ZM, none of them worked. What am I doing wrong?

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Remi_Foicik
New Contributor II

Hello Andressa,

The inputs features class for this tool must be "multipatch" 

You can transform 3d features to multipatch feature class with the geoprocessing tool:
Layer 3D To Feature Class (Couche 3D vers classe d’entités) : ArcGIS Pro | Documentation

Or you can also transform it in City Engine or apply a city engine rule in ArcGIS pro with (if you have the licence) :
Entités des règles CityEngine (3D Analyst) : ArcGIS Pro | Documentation

Rémi

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