topic Re: How to cut and merge many polygons at once in ArcGIS Pro Questions

How to cut and merge many polygons at once

Anonymous User — Fri, 24 Jan 2020 20:57:35 GMT

I was wondering if there was a way to cut polygons using polygons from a different layer as boundaries. And then merging the cut polygons within those boundaries, while preserving attributes of whichever poly had the bigger area.

Basically the goal is to realign the blue and pink layer to the new boundaries(Green Lines)

Re: How to cut and merge many polygons at once

MatthewDriscoll — Fri, 24 Jan 2020 21:10:36 GMT

You will be able to do this with a python script.

Re: How to cut and merge many polygons at once

DanPatterson_Retired — Fri, 24 Jan 2020 21:14:43 GMT

A picture of your situation?

Would a combination of tools work? Like some in the...

An overview of the Overlay toolset—Help | ArcGIS Desktop toolbox or

An overview of the Pairwise Overlay toolset—Help | ArcGIS Desktop

and merge and dissolve-like functions

Re: How to cut and merge many polygons at once

Anonymous User — Fri, 24 Jan 2020 21:26:56 GMT

Any advice on what kind of script? My python skills are not the strongest

Re: How to cut and merge many polygons at once

Anonymous User — Fri, 24 Jan 2020 21:29:04 GMT

I updated the post with a pic of the situation

Re: How to cut and merge many polygons at once

deleted-user-NvcfpBOWaKwr — Fri, 24 Jan 2020 21:33:09 GMT

This is possible. However it could be rather labor intensive if you did it manually. Since you need to do analysis based on the area of each poly before the merge, it would be beneficial to write a python script for the process. I will go over the manual workflow on how I would accomplish this below. If this seems to be too much or your data set is too big, please let me know and I can give you a hand with a python script / tool that will get this done for you.

Step 1:

Create a field within the feature class that will contain the "Area" calculation for each polygon after they are clipped.

I'm sure you know how to do this however just I linked below on how to create, modify and delete fields in ArcGIS Pro.

Fields view—Geodatabases | ArcGIS Desktop

Step2:

Use the clip tool to clip the polygons down based on a "Boundary" layer

This tool can be searched for in the Geoprocessing pane in ArcGIS Pro and I have also linked to the tool documentation.

Clip—Help | ArcGIS Desktop

Step 3:

Do an area calculation on the "Area" field that was created in step one VIA "Calculate Geometry" by right clicking the field name in the attributes table. You can also access the "Calculate Geometry Attributes" tool by searching for it in the Geoprocessing pane.

Step4:

Use the merge tool in the "Edit" ribbon within ArcGIS pro. Select the polygons that you want to merge and preserve the attributes from the polygon with the largest area. You physically have to choose which polygon to preserve the data from within the tool menu. FYI the Merge tool within the "Edit" ribbon in ArcGIS pro is not the same tool that can be found while searching for the merge tool in the Geoprocessing pane. The big difference is that the Merge within the "Edit" pane merges features while the Merge Geoprocessing tool merges datasets.

Let me know if you would like to explore a python script option.

Hope This Helps

Re: How to cut and merge many polygons at once

Anonymous User — Fri, 24 Jan 2020 21:39:51 GMT

Thank you for the great response! I am very interested in exploring a python solution. The layer that needs to be adjusted has around 200,000 features so manually doing it would take quite some time

Re: How to cut and merge many polygons at once

Anonymous User — Fri, 24 Jan 2020 21:48:21 GMT

Here is my thought process on steps so far with the goal of aligning Layer A to Layer B

Cut layer A using layer B
Merge the Layer A polys that are within the Layer B polys, preserving the attributes of the Layer A poly w/ the largest area
If possible, expand the new Layer A polys to the boundaries of the Layer B polys ( For cases where there was no Layer A under Layer B, as in the below pic)

Re: How to cut and merge many polygons at once

deleted-user-NvcfpBOWaKwr — Fri, 24 Jan 2020 22:13:14 GMT

Do features in each layer have information that would match, like a unique identifier, parcel number or something that can be used to match the old geometry to the new geometry?

Re: How to cut and merge many polygons at once

Anonymous User — Fri, 24 Jan 2020 22:19:00 GMT

Yes, the parcel number

Re: How to cut and merge many polygons at once

JohnJones — Fri, 24 Jan 2020 22:22:49 GMT

Another, potentially faster, way of doing this, without any splits or merges, would be based on pairing polygons.

Say you want to align polygons in the 'red' layer to the 'green' layer (for lack of better terminology) one way is to find a label point for each green and red polygon (Feature to Point, inside), for every red point (corresponding to a red polygon) find the nearest green point and match the corresponding polygons (red polygon to the green polygon which has a label point closest to the red polygon's label point) and then transfer the geometry of the green polygon to the red polygon.

For safety you can verify that the mapping is one to one (no to red polygons choose the same green one) and flag any red polygons that match to a conflicting green polygon (you could merge them if desired). If the shifts are large, the label points may shift too much and this won't work well, but if it works it is considerably less work than a bunch of splits & merges.

Re: How to cut and merge many polygons at once

Anonymous User — Fri, 24 Jan 2020 22:33:00 GMT

Good idea! I will give that a shot. So after using the feature to point tool on both layers would I use a python script to find the nearest nearest point of the other layer?

Re: How to cut and merge many polygons at once

deleted-user-NvcfpBOWaKwr — Mon, 27 Jan 2020 15:35:59 GMT

Just to make sure I understand correctly. Essentially what you would like to do is update the geometry of the old parcel boundary layer (blue and pink) with the geometry of the new parcel boundary's (green)

If this is the case then we can make a pretty simple script that can update the geometry of the old layer with the new geometry while preserving the original attributes. Let me know if that is essentially what you are looking to do.

Re: How to cut and merge many polygons at once

Anonymous User — Mon, 27 Jan 2020 16:55:20 GMT

Unfortunately thats not the case. This layer needs the geometry of the green layer but does not have the same attributes. However they do have matching unique ids (APN)

Re: How to cut and merge many polygons at once

deleted-user-NvcfpBOWaKwr — Mon, 27 Jan 2020 18:22:26 GMT

Alright. So the attribute information for the polygon with the largest area after the clip is what you would still keep. If it feels like we are talking in circles, my apologies. Just wanted to make sure I fully understand and to make sure there wasn't possibly an easier solution.

Are you able to share the field names for original layer and the new boundary layer? Tonight Ill start writing up a tool for you to use in pro.

Re: How to cut and merge many polygons at once

Anonymous User — Mon, 27 Jan 2020 19:34:40 GMT

Thank you very much I really appreciate it. Here are the attributes where Layer A needs the geometry of Layer B. Let me know if there's anything else I can provide

Layer A

APN
LAND_CODE1
Reso_nmbr
CNTRL_NMBR
DATE_ADOPT
PROJECT
LANDUSE_1
created_user
created_date
last_edited_user
last_edited_date
Shape.STArea()
Shape.STLength()

Layer B

Shape
GID
APN
APN_DASH
APN10
BOOK
PAGE
BLOCK
PARCEL
ACTION
COMMENTS
INSERT_DATE
PCN_CREATED_BY
PCN_DELETED_BY
WSTATUS
UPDATE_BY
UPDATE_DATE
PRCL_KEY
Shape_Length
Shape_Area

Re: How to cut and merge many polygons at once

deleted-user-NvcfpBOWaKwr — Mon, 27 Jan 2020 20:40:37 GMT

Do you by any chance know what flavor of DB layer A is stored in? MS SQL?

Re: How to cut and merge many polygons at once

Anonymous User — Mon, 27 Jan 2020 20:52:30 GMT

Yes sql

Re: How to cut and merge many polygons at once

deleted-user-NvcfpBOWaKwr — Tue, 28 Jan 2020 17:22:46 GMT

Are you able to export the information in the SQL database to a File Geodatabase? The reason why I'm asking is because I'm reluctant to write code to change information in a SQL database that could be a production database that other services or applications might depend on.

If you were able to export the information into a File Geodatabase we could essentially use that as a test / development database that wouldn't impact anything if something goes wrong. Then once all of the changes have been made and deemed correct you could talk to your DBA about pushing those updates to the SQL database.

Maybe I'm over reacting, however this is how we set up things like this where I work. We setup a Development / Staging Environment then push it to the production environment once everything has been vetted as correct.

Re: How to cut and merge many polygons at once

Anonymous User — Tue, 28 Jan 2020 17:33:51 GMT

Yes that is the same way we operate as well. And yes I can export it to a file geodatabase for testing