Geodatabase Topology in ArcGIS Pro

Topology refers to the spatial relationships and rules that define how features - like points, lines, and polygons- interact with each other. It ensures data integrity by enforcing rules such as "no gaps," "no overlaps," or "lines must connect at endpoints."

In a dataset of wild rice beds, topology can help guarantee that:

Rice beds don't accidentally overlap each other
There are no unintentional gaps between areas
Boundaries are shared cleanly between adjacent polygons

Using topology helps you validate, clean, and maintain high-quality spatial data - which is essential for accurate analysis and decision-making.

Software requirement(s):

ArcGIS Pro 3.4.x

Geodatabase Download: https://tribalgis-my.sharepoint.com/:f:/p/sarques/EpiYxa8Xd-dKhDV7dM8o6_oBxgSI2ZYDH0_8i9KiVdZvag?e=7XVxkI

Disclaimer: The dataset included in this article is entirely fictional and is intended for instructional purposes only. The data does not represent actual wild rice bed's locations. Any resemblance to real locations, practices, or communities is purely coincidental. Please consult with appropriate tribal representatives or cultural authorities before working with or referencing indigenous knowledge or cultural resources in GIS projects.

Steps

Create a polygon feature class for wild rice beds
Set up a topology to ensure clean geometry and logical spatial relationships
Apply and validate topology rules
Fix topology errors

Step 1 – Create a New File Geodatabase

Open ArcGIS Pro and create a new map project.
In the Catalog pane, right-click the Databases folder > New > New File Geodatabase (you can also use the default geodatabase that was created with your new project).

Name it: WildRice_MN.gdb

Step 2 – Create a Feature Dataset

Right-click the geodatabase > New > Feature Dataset

Name it: WildRice_Beds
Set the coordinate system (Recommended: NAD 1983 UTM Zone 15N)

Click Run

Feature datasets are required for topology creation and ensure all feature classes use the same coordinate system.

Step 3 – Create a Polygon Feature Class

Right-click the feature dataset > New > Feature Class

Name: WildRice_Polygons
Alias: Wild Rice beds
Feature Type: Polygon
Click Next, add these fields:
- Name (Text, 50)
- WaterBody (Text, 50)
- SurveyDate (Date)

Click Next a few times (accept default values) and Finish

Step 4 – Add Sample Data

You can draw a few wild rice beds manually (Edit > Create Features) or use the sample dataset provided.

Step 5 – Create Topology

Right-click the WildRice_Beds feature dataset > New > Topology

Name: WildRiceTopology
Add your feature class WildRice_Polygons or Wild_Rice_Beds or another name
Set cluster tolerance to default (0.001 meters)

Add the following rules:
- Must Not Have Gaps (ensures no space between rice beds)
- Must Not Overlap (rice beds shouldn’t occupy same space)
- (Optional) Must Be Covered By WaterBody layer (if you have a hydro layer)

Click Next and check your Summary

Click Finish. Your topology is added to your Feature dataset (if you don't see it, right-click on the WildRice_Beds feature dataset and select Refresh).

Step 6 – Validate the Topology

Add the topology layer to your map from the Catalog (drag and drop)

Go to the Catalog pane > Expand your File Geodatabase and the Feature Dataset
Right-click WildRiceTopology > Validate

Use the Error Inspector from the Edit tab to view and inspect errors

If you've already validated your topology and there are no errors, the Error Inspector will appear empty.

The Error Table (bottom left panel) lists all topology errors, including:

Rule violated (e.g., Must Not Overlap)
Feature Class and ID

The bottom right panel:

Preview: Highlights the error location on the map
Details: Lists the involved feature IDs and geometry
Fix: Lets you interactively fix, merge, clip, create feature, or mark as exception.

Step 7 – Fix Topology Errors

Use tools like:

Modify Features > Reshape to clean overlaps
Merge to combine adjacent beds
Cut or Clip for overly large beds
Construct Polygons (Advanced) to fill gaps

Step 8 – Save and Re-Validate

After each edit, revalidate your topology to ensure all rules are enforced.

Step 9 - Mini Exercise: Test Topology by Creating an Overlap Error

On the Edit tab, in the Features group, click Create

Select the Wild Rice Beds template (your feature name may be different)

Draw a new polygon that overlaps an existing rice bed (it can partially or completely cover an existing one)

Save your Edits

In the Catalog pane, right-click your topology > Validate

Now you can see that the Error Inspector is displaying the topology error you just created. It highlights the overlapping area and shows details such as the violated rule ("Must Not Overlap"), the involved features, and options to fix or mark the error as an exception.

Fix the errors (optional)
Save your edits, and save your project

Topology is a powerful QA/QC tool when working with complex polygon datasets.
You can export fixed features to a clean polygon layer for use in dashboards or maps.
Optionally, use topology rules with multiple feature classes (e.g., RiceBeds and HydroPolygons).

We hope that this article has been helpful! If you have any feedback or questions, please feel free to send us an email or connect with us for a chat. The NTGISC team is here to assist you further!