topic Re: Large polygons contain many smaller polygons in ArcGIS Pro Questions

Large polygons contain many smaller polygons

Pia — Wed, 31 Jan 2024 10:50:17 GMT

Hi there!

I've got a question about how to bring several bigger polygons which each contain smaller polygons together. They both have the same columns but the information they carry is on a greater level/scale.

Background: I have 5 Layers. 3 Layers with Nuts 1-3 Levels, and 2 Layers with Gaul 1-2 Levels (Global Administrative Unit Layers). I already split them up to continents to reduce their size. Each polygon (on whatever level) contains information about the count of x. So if I just map it as it is, it counts the occurence of x double, both for gaul1 and gaul2 for example.

Is there a tool in ArcGIS Pro, Geopandas , etc. where I can have one layer for each continent without loosing the information of the lower level? Right now I have one layer containing Nuts1-3 and gaul1-2, the Shape_Area & Shape_Length columns are only populated for the corresponding Level otherwise its empty.

And if that is not possible, how can I bring Nuts1-3 and gaul1-2 together? I do have the spatial information of both of them but sometimes gaul2 shows smaller polygons and sometimes Nuts3 and so on..

I hope this post is not too confusing... Thank you all for your help!

Re: Large polygons contain many smaller polygons

Ed_ — Wed, 31 Jan 2024 13:27:27 GMT

I think some screenshots of your input data and what you are trying achieve might help understanding your question better.

Re: Large polygons contain many smaller polygons

DanPatterson — Wed, 31 Jan 2024 13:35:27 GMT

Have you looked at the 'overlay' toolset?

perhaps apportion, union, intersect, update or spatial join will accomplish singularly or in tandem will accomplish what you want to do.

An overview of the Overlay toolset—ArcGIS Pro | Documentation

Re: Large polygons contain many smaller polygons

DavidPike — Wed, 31 Jan 2024 20:38:27 GMT

The post is very confusing for me unfortunately. I'd recommend adding some graphics for us visually-minded folks.

Re: Large polygons contain many smaller polygons

Pia — Thu, 01 Feb 2024 09:31:40 GMT

Blue= Gaul2 Layer, Black = Gaul1Layer

Thank you for the reply! I hope this screenshot helps. Some information is only stored in Gaul1 and some only in Gaul2.

Re: Large polygons contain many smaller polygons

Ed_ — Thu, 01 Feb 2024 12:58:38 GMT

@Pia thank you for sharing additional info, so are you trying to join the attributes of gaul 1 and gaul 2? If so then the `Spatial Join` tool can help you with that but if you want to join them and get a layer that shows their respective geometries as well then may be use the `Union` tool.

Re: Large polygons contain many smaller polygons

DanPatterson — Thu, 01 Feb 2024 14:06:06 GMT

Did you try one of the overlay tools as suggested?

If you want to include the geometry as well, try union

If you want to include the attributes only, then spatial join

PS experiment on copies of the files

Re: Large polygons contain many smaller polygons

Pia — Mon, 05 Feb 2024 08:02:40 GMT

I did, thank you! Union might be the tool for me as I don't want to loose any information and want to keep the smallest possible polygon. But the result is 5 columns in my new dataset called "deseases" (That's what I want to map). Is there a way how I can join those columns and still keep all the information? Because if I do it with Spatial Join I have to decide on what level I want to map....

Re: Large polygons contain many smaller polygons

DanPatterson — Mon, 05 Feb 2024 10:35:26 GMT

You need to carefully read the documentation for Union to select the tool parameters to get the attributes as you want them

Union (Analysis)—ArcGIS Pro | Documentation

The images in

How Union works—ArcGIS Pro | Documentation

will help

Also, once your output is derived, you can always add a new field and use appropriate field calculations to combine the what you need into a single column.