6.1 Vector Analysis: Overlay Tools (Intersect, Union, Erase, Identity, Clip)

Esri ArcGIS Pro Associate Certification Exam Exam

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1 Chapter 1: Introduction & Exam Overview

1.1 ArcGIS Pro Associate (EAPA_2025) Exam Structure & Logistics 1.2 How to Study for the ArcGIS Pro Associate Certification

2 Chapter 2: Data Models & Geodatabase Architecture

2.1 Geospatial Data Models (Vector, Raster, Tabular, and TIN) 2.2 Geodatabase Architecture (File, Enterprise, Mobile, and Feature Datasets) 2.3 Coordinate Systems, Datums, and Projected Coordinate Systems 2.4 Geographic Transformations and Spatial References

3 Chapter 3: Data Integrity & Schema Management

3.1 Attribute Domains (Coded Value and Range Domains) 3.2 Subtypes and Feature Class Schema Design 3.3 Geodatabase Topology and Validation Rules 3.4 Metadata Standards, Editing Tools, and CAD/BIM Integration

4 Chapter 4: Layer Symbology & Display

4.1 Vector Symbology Methods (Single Symbol, Unique Values, Graduated/Unclassed Colors, Proportional Symbols) 4.2 Raster Symbology and Stretch Types (Min-Max, Standard Deviation, Percent Clip, Colormap) 4.3 Text and Labeling with the Maplex Label Engine 4.4 Dynamic Labeling with Arcade Expressions

5 Chapter 5: Advanced Visualization & Display Properties

5.1 Definition Queries & Display Filters 5.2 Scale Ranges & Performance 5.3 3D Visualization & Scenes 5.4 Temporal Visualization & Time Layers

6 Chapter 6: Vector & Proximity Spatial Analysis

6.1 Vector Analysis: Overlay Tools (Intersect, Union, Erase, Identity, Clip) 6.2 Vector Analysis: Proximity Tools (Buffer, Near, Generate Near Table, Spatial Join) 6.3 Attribute Joins, Relates, and Relationship Classes 6.4 Selection Methods: Select By Location vs. Select By Attributes

7 Chapter 7: Advanced Analysis & Geoprocessing

7.1 Geoprocessing Environment Settings 7.2 Raster Surface Analysis 7.3 Spatial Statistics & Pattern Analysis 7.4 Geoprocessing Automation: ModelBuilder and ArcPy

8 Chapter 8: Map Layouts & Map Series

8.1 Page Layout Composition and Design Elements (Scale Bars, Legends, North Arrows) 8.2 Map Series Creation (Spatial vs. Bookmark Map Series) 8.3 Exporting Maps and Layouts (PDF, PNG, JPEG, PDF Layers, Color Profiles)

9 Chapter 9: Publishing & Package Sharing

9.1 Sharing Web Maps, Web Scenes, and Portal/ArcGIS Online Publishing 9.2 Web Layers and Services (Web Feature Layers, Vector Tile Layers, Map Image Layers) 9.3 Geospatial Packages (Map Packages, Project Packages, Geoprocessing Packages)

6.1 Vector Analysis: Overlay Tools (Intersect, Union, Erase, Identity, Clip)

Key Takeaways Explain This Topic AI

Intersect computes the geometric intersection of all inputs, preserving attributes from all input features but retaining only overlapping areas.

Union computes a geometric union of all inputs, requires polygon inputs exclusively, and preserves all features and their attributes.

Erase removes portions of the input features that fall within the erase features, transferring no attributes from the erase layer.

Identity computes a geometric intersection of the input features and identity features, retaining all input features while appending overlapping identity attributes.

Clip extracts input features that overlay the clip features without combining attributes, functioning purely as an extraction mechanism.

Last updated: July 2026

Vector Analysis: Overlay Tools in ArcGIS Pro 3.x

Vector overlay operations form the backbone of spatial analysis in Geographic Information Systems. In ArcGIS Pro 3.x, these tools allow analysts to superimpose two or more feature classes to create a new output feature class. This new dataset combines the geometries and, depending on the tool chosen, the attributes of the inputs.

For the EAPA_2025 exam, you must have an intimate understanding of the geometric outcomes and tabular behaviors of the five primary overlay tools: Intersect, Union, Erase, Identity, and Clip.

1. Intersect

The Intersect tool computes a geometric intersection of the input features. Features or portions of features that overlap in all layers and/or feature classes will be written to the output feature class.

Geometric and Tabular Behavior

Geometry: Only the overlapping areas are preserved. If no features overlap, the output will be empty.

Attributes: The output contains attributes from all input feature classes.

Inputs: Can accept points, lines, or polygons.

Output Geometry Type: The output geometry type must be the same dimension as or lower than the input with the lowest dimension. For example, intersecting a line layer and a polygon layer results in a line or a point layer, but never a polygon layer.

Step-by-Step Workflow in ArcGIS Pro 3.x

Navigate to the Analysis tab and click Tools to open the Geoprocessing pane.

Search for and open the Intersect tool (Analysis Tools > Extract).

In the Input Features parameter, add the layers you wish to intersect. The order of inputs does not affect the geometric output but can dictate attribute order.

Specify the Output Feature Class in your project geodatabase.

(Optional) Adjust the Attributes To Join parameter. The default is 'All', meaning all attributes are transferred.

Run the tool.

Exam Tip: When a scenario asks you to find areas where multiple conditions co-exist (e.g., areas that are both forested AND have steep slopes) and you need the attributes of both layers for subsequent analysis, Intersect is the correct tool.

2. Union

The Union tool computes a geometric union of the input features. All features and their attributes will be written to the output feature class.

Geometric and Tabular Behavior

Geometry: The full extent of all input features is preserved. Where features overlap, new intersecting geometries are created.

Attributes: The output contains attributes from all input feature classes. For areas where a feature from one input does not overlap with a feature from another input, the attributes for the missing feature will be set to Null.

Inputs: Requires all input feature classes to be polygons . This is a strict requirement.

Output Geometry Type: Always polygons.

Edge Cases and Environment Settings

If you perform a Union and notice small, unintended sliver polygons, you may need to adjust the XY Tolerance environment setting. A larger XY tolerance forces vertices that are very close together to snap to one another, eliminating micro-slivers.

3. Erase

The Erase tool creates a feature class by overlaying the Input Features with the polygons of the Erase Features. Only those portions of the input features falling outside the erase features' boundaries are copied to the output.

Geometric and Tabular Behavior

Geometry: Portions of the input features that overlap the erase features are removed.

Attributes: Only the attributes of the Input Features are preserved. Attributes from the Erase Features are strictly ignored.

Inputs: Input features can be point, line, or polygon. Erase features must be polygons (or have the same or higher dimension than the input).

Exam Tip: Erase is heavily utilized in suitability models to exclude restricted areas. For instance, if you are finding suitable development parcels, you would erase wetlands, steep slopes, and protected habitats from your study area.

4. Identity

The Identity tool computes a geometric intersection of the input features and identity features. The input features or portions thereof that overlap identity features will acquire the attributes of those identity features.

Geometric and Tabular Behavior

Geometry: All input features are preserved. Where they overlap with identity features, new geometries are created based on the intersection boundary.

Attributes: The output combines the attributes of the input features and the overlapping identity features. Input features not overlapping identity features retain only their original attributes (with nulls for the identity fields).

Inputs: Input features can be point, line, or polygon. Identity features must be polygons.

5. Clip

The Clip tool extracts input features that overlay the clip features. Think of it as a cookie cutter.

Geometric and Tabular Behavior

Geometry: Only the input features falling within the clip features are preserved. Their geometry is trimmed to the exact boundary of the clip features.

Attributes: Only the attributes of the Input Features are preserved. Clip does not combine or join attributes.

Inputs: Input features can be point, line, or polygon. Clip features must be polygons.

Tool Comparison Matrix

Tool Preserved Geometry Preserved Attributes Input Requirements
Intersect Overlap only Both inputs Any geometry combination
Union All inputs Both inputs Polygons only
Erase Non-overlapping input Input only Erase features must be polygons
Identity All input Input + overlapping identity Identity features must be polygons
Clip Overlapping input Input only Clip features must be polygons