topic Re: Python script to find out if two layers are overlapping in Python Questions

Python script to find out if two layers are overlapping

Anonymous User — Tue, 07 Jan 2020 18:57:38 GMT

As part of QAQC, I have to routinely check if all vector line data is buffered on the buffered layer. The layers are: vector line layer, buffer layer, and grid number layer. As of right now, I scan the entire county boundary to see if there is any vector line data that is not buffered on the buffer layer. If it is not buffered, I need to find out which grid number the problem resides.

I would like to make a python script that would check to see if all vector line data (layer 1) is overlaying the buffered layer (layer 2) and if not, which grid number (layer 3) is the problem.

Does anyone have any experience trying to write a python script that can tell if one layer is spatially overlaying another layer?

Code examples would be much appreciated.

Re: Python script to find out if two layers are overlapping

JoeBorgione — Tue, 07 Jan 2020 19:16:04 GMT

I haven't done it specifically, but a spatial selection or a series of them ought to do the trick

Re: Python script to find out if two layers are overlapping

XanderBakker — Wed, 08 Jan 2020 15:28:23 GMT

Hi ggroshans_GreenvilleWater ,

Can you provide a screenshot showing the lines, buffers and grids or provide a sample of your data? There are a couple of things that might complicate this and I would like to see some specific situations to see what would be possible.

Re: Python script to find out if two layers are overlapping

Anonymous User — Wed, 08 Jan 2020 15:57:39 GMT

Hi Xander,

Thank you for your help. I have attached three screenshots. 1) A view of the vector line data, the buffer layer, and an example of how the vector line data may not correspond to the buffer layer, 2) A screenshot of my table of contents, and 3) A zoomed out view to show the grid layer (e.g., screenshot 1 is within grid 38).

Re: Python script to find out if two layers are overlapping

AndrewLaws2 — Wed, 08 Jan 2020 16:45:05 GMT

Hi, I use a similar script from the Python window in ArcMap

##running from Python window in ArcMap with layers already MXD and using layer names as per your post

import arcpy

arcpy.SelectLayerByLocation_management('layer1', "WITHIN", 'layer2')

arcpy.SelectLayerByLocation_management('layer1', "", "", "", "SWITCH_SELECTION")

arcpy.SelectLayerByLocation_management('layer3', "INTERSECT", 'layer1')

fc = 'layer3'
field = 'layer3_field_that_contains_grid_name'
cursor = arcpy.SearchCursor(fc)
for row in cursor:
print(row.getValue(field))

Re: Python script to find out if two layers are overlapping

AndrewLaws2 — Wed, 08 Jan 2020 16:46:10 GMT

What's the name of the labeling field in mapnum_copy?

Re: Python script to find out if two layers are overlapping

JoeBorgione — Fri, 10 Dec 2021 20:02:16 GMT

Using the syntax highlighter makes code reading much easier:

##running from Python window in ArcMap with layers already MXD and using layer names as per your post

import arcpy

arcpy.SelectLayerByLocation_management('layer1', "WITHIN", 'layer2')

arcpy.SelectLayerByLocation_management('layer1', "", "", "", "SWITCH_SELECTION")

arcpy.SelectLayerByLocation_management('layer3', "INTERSECT", 'layer1')

fc = 'layer3'
field = 'layer3_field_that_contains_grid_name'
cursor = arcpy.SearchCursor(fc)
for row in cursor:‍‍‍‍‍‍‍‍‍‍‍‍‍‍

Re: Python script to find out if two layers are overlapping

AndrewLaws2 — Wed, 08 Jan 2020 16:52:33 GMT

Can you tell it's my first time posting code to Geonet haha. Thank you for highlighting this to me.

Re: Python script to find out if two layers are overlapping

AndrewLaws2 — Wed, 08 Jan 2020 16:54:59 GMT

What's the field name used in mapnum_copy for labelling?

Re: Python script to find out if two layers are overlapping

Anonymous User — Wed, 08 Jan 2020 21:19:26 GMT

Thanks for all your help so far. The field name used in mapnum_copy for labeling is called MapNum

Re: Python script to find out if two layers are overlapping

Anonymous User — Wed, 08 Jan 2020 21:21:56 GMT

Thanks so much for the code example.

Unfortunately, after running the SelectLayerByLocation_management function, I get an error stating, "ERROR 000368: Invalid input data."

After googling, it says SelectLayerByLocation requires a layer to select features so you cant select features directly on a feature class. Would this be solved by a preceding MakeFeatureLayer function?

Re: Python script to find out if two layers are overlapping

JoeBorgione — Wed, 08 Jan 2020 21:23:02 GMT

Yep.

Re: Python script to find out if two layers are overlapping

AndrewLaws2 — Wed, 08 Jan 2020 21:24:44 GMT

Yes, it would. You may have to do it for each layer you are gonna do.

Re: Python script to find out if two layers are overlapping

AndrewLaws2 — Fri, 10 Dec 2021 20:02:19 GMT

import arcpy

arcpy.MakeFeatureLayer_management('water_main_copy', 'water_main_copy_lyr')

arcpy.SelectLayerByLocation_management('water_main_copy_lyr', "WITHIN", 'water_main_buffer')

arcpy.SelectLayerByLocation_management('water_main_copy', "", "", "", "SWITCH_SELECTION")

arcpy.SelectLayerByLocation_management('mapnum_copy', "INTERSECT", 'water_main_copy')

fc = 'mapnum_copy'
field = 'MapNum'
cursor = arcpy.SearchCursor(fc)
for row in cursor:
    print(row.getValue(field))
‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍

This would be a way to make a feature layer. Give it a try and if it gives you errors just follow the similar naming convention for feature layers for water_main_buffer and mapnum_copy.

The text that comes will be the Map Numbers with unbuffered water mains.

Hope this helps!