topic Re: Small vs big Polygon overlap on a Map Question in ArcGIS Pro Questions

Small vs big Polygon overlap on a Map Question

DEAF_PROBERT_68 — Mon, 14 Feb 2022 14:33:07 GMT

Hi ,

I have been searching or google for a map that shows two polygons with no luck. What I want is to look at a map or maps where there are two polygons that overlap each other. What I mean is if there is a small polygon that is under a big polygon. Are there examples that can I look at ? and if so what is the workflow for that ?

I hope this is not a hard question to ask .

Re: Small vs big Polygon overlap on a Map Question

shan_sarkar — Mon, 14 Feb 2022 05:26:27 GMT

Hi @DEAF_PROBERT_68 ,

Do you mean you want a bigger polygon to overlap with a smaller polygon, with the bigger polygon being the top most layer and the smaller polygon being the underlaying layer?

If you using simply looking for an sample you can use the Template data that comes along with the ArcGIS Desktop installation. Ideally the data is located at C:\Program Files (x86)\ArcGIS\Desktop10.8\TemplateData.

This contains 2 datasets one for the basic world data and basic US data with state boundaries and county boundaries.

I hope this helps.

Re: Small vs big Polygon overlap on a Map Question

DanPatterson — Mon, 14 Feb 2022 05:41:02 GMT

2 quick methods.

- symbolize the polygons with no fill, just an outline

- produce a featureclass which sorts the geometry based on the shape_area field in descending order or area, so big things get mapped first then smaller things on top.

Sort (Data Management)—ArcGIS Pro | Documentation

Re: Small vs big Polygon overlap on a Map Question

DEAF_PROBERT_68 — Mon, 14 Feb 2022 14:32:06 GMT

Yes, you are correct .

Re: Small vs big Polygon overlap on a Map Question

DEAF_PROBERT_68 — Mon, 14 Feb 2022 15:06:48 GMT

@JohnMNelson

Your thoughts on this for Cartography or Map-making ?

Re: Small vs big Polygon overlap on a Map Question

JohnNelsonEsri — Mon, 14 Feb 2022 15:25:02 GMT

occlusion is a persistent challenge in cartography. somethings bigger things just cover up the smaller things. if you have a map where this is happening, you could consider some options for the polygon fill. the most basic option is to set the fills to be semi-transparent so that overlapped content is still largely visible. another option is to experiment with blend modes for the topmost layer and make a clever legend describing what the overlapping areas look like. but i would consider using a hatched fill for your layers so that they were visible in all cases. for example, i used hatched fills of different colors and hatch orientation to show individual, and overlapping, species ranges in this map: https://adventuresinmapping.com/2016/06/09/how-to-sharknado-map/

Re: Small vs big Polygon overlap on a Map Question

DEAF_PROBERT_68 — Mon, 14 Feb 2022 16:57:25 GMT

Thank you John. So is that the word you token as "Occlusion" maps where there is a small polygon is hidden by a bigger polygon ?

Re: Small vs big Polygon overlap on a Map Question

JohnNelsonEsri — Mon, 14 Feb 2022 17:26:16 GMT

yes, occlusion is just the general issue when one thing covers up another thing. when working with several layers it can become a challenge. it's a very large challenge in 3D mapping, where elements in the foreground tend to obscure elements in the background.

Re: Small vs big Polygon overlap on a Map Question

DEAF_PROBERT_68 — Mon, 14 Feb 2022 17:33:09 GMT

Has that word been around in years or is it just pop up a new terminology recently. I need to grab a cartography book HA HA HA ....

Re: Small vs big Polygon overlap on a Map Question

DEAF_PROBERT_68 — Wed, 16 Feb 2022 01:43:50 GMT

I couldn't find the book I have but I did went over here. https://oer.galileo.usg.edu/geo-textbooks/3/

and did not find any word you mention "Occlusion"

Re: Small vs big Polygon overlap on a Map Question

JohnNelsonEsri — Wed, 16 Feb 2022 12:39:03 GMT

well I guess you'll just have to trust me that it's a word I guess! 🙂

regardless of terminology, do any of the strategies I describe above sound helpful in your circumstance?

Re: Small vs big Polygon overlap on a Map Question

DEAF_PROBERT_68 — Sat, 19 Feb 2022 01:41:59 GMT

Not yet read it since I have been really busy lately. Starting a new project on AGOL for historical aerial photo project on my forest.... I will get a chance to read it this weekend.

Re: Small vs big Polygon overlap on a Map Question

GregBenskin — Fri, 27 Jan 2023 13:39:10 GMT

Here is how I go about it.

Potential Synopsys: Lets say for example you have a sports complex. The entire complex may be represented by a large polygon, while you would like the club house to be situated on the complex polygon and the club house kitchen on the club house polygon. But when one views the layer the large polygon overshadows all the smaller ones making it difficult or impossible to view.

This is what you could do to correct the issue within ARC View or ARC Editor:

1.) Click on the layer you wish to display

2.) right click while on the layer and select Properties

3.) Layer Properties will appear, Select the 5th Tab from the right called Symbology

4.) Select Unique Symbology and Adjust Symbols or Color Choices according to your needs

5.) Select Advanced at the bottom of the page (See Below then move down for step 6.)

Step 6.) once you have selected Advanced you will be able to Select Symbol Levels and set the priority in which various categories in your layer may be displayed. Polygons you wish to display at the top or visually above, should be given the higher numbers while Larger polygons with lower visual priority are given lower numbers. [In this case I wanted the Community Centre to appear above the Stadium and the stadium above the Complex]

The Result: