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!