topic Create current status for a layer of overlap polygons in ArcGIS Pro Questions

Create current status for a layer of overlap polygons

mody_buchbinder — Thu, 16 Feb 2023 08:02:01 GMT

I have a polygon layer with many overlap polygons, each one have a time stamp.

I would like to create a "current status" polygon layer that will not have overlap and each polygon will be the latest.

Some polygons that have partially overlap will be changed.

For example I have one polygon from 2020 that have cross polygon from 2019 and anther cross polygon from 2021

The 2020 polygon will be cut by 2021 polygon but not by 2019 polygon.

The only way I could think about is to take the polygons from the original layer one by one the oldest to the newest, with each one to to an Erase and Append on the result layer.

Is there any better way?

Re: Create current status for a layer of overlap polygons

JohannesLindner — Thu, 16 Feb 2023 08:41:44 GMT

You can probably whip up some Python script.

But this part is very unclear:

Some polygons that have partially overlap will be changed.
For example I have one polygon from 2020 that have cross polygon from 2019 and anther cross polygon from 2021
The 2020 polygon will be cut by 2021 polygon but not by 2019 polygon.

Can you clarify that, maybe with a sketch?

Re: Create current status for a layer of overlap polygons

mody_buchbinder — Thu, 16 Feb 2023 15:27:51 GMT

At the top the layer I have, at the bottom the layer I would like to create

Thanks

Re: Create current status for a layer of overlap polygons

JohannesLindner — Thu, 16 Feb 2023 17:12:07 GMT

That sketch helped alot.

It turns out to be relatively easy:

# parameters polygon_fc = "TestPolygons" id_field = "IntegerField" date_field = "DateField" out_path = "memory/CurrentState" # copy the feature class out_fc = arcpy.management.CopyFeatures(polygon_fc, out_path) # read the input fc fields = [id_field, date_field, "SHAPE@"] polygons = [dict(zip(fields, row)) for row in arcpy.da.SearchCursor(polygon_fc, fields) ] # get unique ids unique_ids = {p[id_field] for p in polygons } # iterate over the unique ids for uid in unique_ids: # get all states of that polygon, sort by date states = [p for p in polygons if p[id_field] == uid ] states.sort(key=lambda s: s[date_field]) # start updating the output fc for this id with arcpy.da.UpdateCursor(out_fc, ["SHAPE@"], where_clause=f"{id_field} = {uid}", sql_clause=[None, f"ORDER BY {date_field}"]) as cursor: # cursor and states are in the same order (oldest to newest) for i, row in enumerate(cursor): # get the geometry of this row state_geometry = states[i]["SHAPE@"] # == row[0] # erase/subtract each newer state for k in range(i+1, len(states)): newer_state_geometry = states[k]["SHAPE@"] state_geometry -= newer_state_geometry # we can use "-" to get the difference between two polygons # update the geometry cursor.updateRow([state_geometry])

Original:

Current state:

Re: Create current status for a layer of overlap polygons

mody_buchbinder — Thu, 23 Feb 2023 05:49:59 GMT

It is a nice code. I did not know I can use minus on geometry.

It is after all doing the erase and append that I suggested

Thanks