Merging Feature Classes in ArcGIS Pro

• Merging land use data from different years to analyze changes over time.
• Integrating different administrative boundary shapefiles (e.g., city, county, state boundaries) into a single dataset.
• Combining river networks, lakes, and watershed boundaries into a unified hydrological dataset.
• Merging vegetation or habitat maps from different surveys or studies.

The project includes two soil maps and two standalone tables that cover a small area located between Leech Lake and Lake Winnibigoshish in the Chippewa National Forest (MN).

The Add Join tool allows you to join a table to a feature layer or another table based on a common field. Here are the options you need to configure:

Input Table

This is the feature layer or table that you want to enhance with additional attributes from another table.

Input Field

This is the field in the input table that you will use to join with the join table.

Join Table

This is the table that contains the additional attributes you want to bring into the input table.

Join Field

This is the field in the join table that matches the input field in the input table.

Keep All Input Records

This option determines whether to keep all records in the input table, regardless of whether they have matching records in the join table.

Index Join Fields

This option creates an index on the join fields to improve performance, especially with large datasets. Check this if you are working with large datasets or if you will perform multiple joins on the same fields.

Join Operation

Specifies how to handle records that do not match (e.g., "KEEP_COMMON" to keep only matching records). Choose based on whether you want to keep all records or only matching records (see yellow callout for more information below).

Validate Join

Validates the join operation to ensure that it can be completed successfully. Enable this to check for potential issues before performing the join.

Add Source Information to Output Option

The option to Add source information to output allows you to include additional fields in the output feature class that indicate the origin of each merged record.

These fields typically include:

• Source_FID: The ObjectID (or unique identifier) from the original feature class.
• Source_NAME: The name of the original feature class from which the record came.

Purpose and Benefits

• Adding source information helps trace back which original dataset each feature in the merged output came from. This is particularly useful for quality control, debugging, and understanding the lineage of your data.
• It aids in managing and documenting the merged data, especially if you are combining datasets from multiple sources with potentially overlapping or conflicting information.
• It allows for differentiated analysis or visualization based on the source. For example, you can color-code or filter features based on their original source.

When to Use It?

• Use this option if you need to document the source of each feature for transparency or reporting purposes.
• If you are concerned about the quality or consistency of data from different sources, having source information can help you identify and address issues.
• If you plan to analyze the merged data based on its original sources, adding source information will facilitate such analyses.

When You Might Not Need It?

• If the datasets you are merging are very similar and you do not need to differentiate between them later, you might not need this additional information.
• If you prefer a simpler output without extra fields, especially if the source information is not crucial for your current project.

Alternatively, if you want to remove the line without using the Remove Overlap tool, you can try the following methods:

Dissolve Tool

The Dissolve tool can be used to combine adjacent polygons that share a common attribute into a single polygon, effectively removing the boundary lines between them.

1. Open the Dissolve tool (Analysis > Tools > Data Management > Generalization > Dissolve).

2. Select your merged feature class as the input.

3. Choose an appropriate field (or no field) for the Dissolve Fields parameter if you want to dissolve all boundaries.

4. Run the tool to create a new feature class with dissolved boundaries.

Editing Tools

Manual editing using the editing tools allows you to merge polygons by removing the boundary line.

1. Start an editing session.

2. Use the Edit Vertices tool to manually adjust the vertices of the polygons to remove the line.

3. Use the Union tool under the Modify Features pane to combine the polygons.

4. Save your edits.

Union Tool

The Union tool can be used to combine overlapping polygons from different layers into one feature class, which can help in managing overlaps and removing boundaries.

1. Open the Union tool (Analysis > Tools > Overlay > Union).

2. Select your merged feature class as the input.

3. Run the tool to create a new feature class where overlapping areas are handled.

By using these methods, you can remove the boundary line between your map units and create a more seamless merged feature class without relying solely on the Remove Overlap tool.

Methods

Center Line Method

This method creates a line halfway between the overlapping polygon boundaries and splits the overlap along this line. Best suited for cases where you want a balanced distribution of the overlap area between the polygons. This is often used in scenarios where the overlap area is considered to equally belong to both polygons, such as administrative boundaries or property lines.

Thiessen Overlap Method

This method assigns the overlapping area to the closest polygon based on the perpendicular distance to the edges of the polygons. The resulting boundary is adjusted to maintain proximity relationships. Ideal for scenarios where the proximity to the original polygons is important. This method is commonly used in hydrological modeling, resource allocation, or any situation where the closest feature should dictate the boundary.

Grid Overlap Method

This method divides the overlap area using a grid-based approach. It systematically allocates sections of the overlap to the adjacent polygons based on a grid. Useful for large datasets where a systematic and computationally efficient approach is needed. It can also be beneficial when the overlap needs to be divided in a regular pattern, such as in environmental modeling or large-scale land cover studies.

When to Use Each Method?

Center Line Method

• You need a fair and balanced division of the overlap area.
• The overlap area should be shared equally.
• Precision in maintaining the middle line is crucial.

Examples: Administrative boundaries, property lines, Urban planning boundaries.

Thiessen Overlap Method

• The proximity of polygons is important for the analysis.
• You want the closest polygon to "claim" the overlap area.
• Maintaining natural boundaries is essential.

Examples: Hydrological studies, natural resource allocation, ecological or habitat boundaries.

Grid Overlap Method

• You need a method that scales well with large datasets.
• The overlap should be divided systematically.
• Regular pattern division is acceptable or preferred.

Examples: Large-scale environmental studies, land cover and land use analysis, agricultural or forestry planning.

Key Considerations when Merging Shapefiles

Geometries

Ensure that the geometries (points, lines, polygons) of the feature classes you are merging are the same. You cannot merge a point feature class with a polygon feature class.

Coordinate Systems

All feature classes should have the same coordinate system. If they don't, reproject them to a common coordinate system before merging.

Attribute Fields

Ensure that the attribute fields (columns) you want to preserve are compatible. You may need to harmonize field names and data types. For instance, if one shapefile has a field named Soil_Type and another has SoilClass, you should rename them to match.

Field Mapping:

Use the "Field Map" option in the Merge tool to manage how fields from different feature classes are combined. You can choose to keep or discard certain fields and specify how values should be handled.