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Join

This tool allows you to combine data from two layers based on attribute matching or spatial relationships. This is essential for spatial analysis, data enrichment, and creating comprehensive datasets.

1. Explanation​

Joining is the process of attaching fields from one layer (Join Layer) to another layer (Target Layer).

GOAT supports three types of joins:

  1. Attribute Join: Matches features based on a common field (e.g., matching "Zip Code" in both layers).
  2. Spatial Join: Matches features based on their geometric relationship (e.g., "features that intersect" or "features within a distance").
  3. Spatial & Attribute Join: Requires both a spatial overlap and a matching attribute to join features.

The result is a new layer containing the Target Layer's geometry and attributes, plus the attributes from the Join Layer.

2. Example use cases​

Attribute Join​

  • Add population data to zip code areas (matching on zip code).
  • Combine survey data with census tract boundaries (matching on tract ID).

Spatial Join​

  • Count the number of schools within each city district (Points inside Polygons).
  • Find the closest fire station to each building.
  • Sum the total length of roads within a park.

3. How to use the tool?​

1
Click on Toolbox Options.
2
Under the Data Management menu, click on Join.

Select layers​

3
Select your Target Layer: The main layer you want to keep.
4
Select your Join Layer: The layer containing data you want to add.

Choose Join Method​

5
Select the Join Method:
  • Attribute: Match based on fields.
  • Spatial: Match based on location.
  • Spatial & Attribute: Match based on both.

Settings (depending on method)​

If Attribute Join:

  • Select the Target Field (key in matching layer).
  • Select the Join Field (key in join layer).

If Spatial Join:

  • Select the Spatial Relationship (e.g., Intersects, Within Distance, Completely Contains).
  • If "Within Distance", specify the search distance and units.

Join Options (Cardinality)​

6
Select the Join Operation (One-to-One or One-to-Many).

One-to-One: If multiple features in the Join Layer match a single feature in the Target Layer, you must choose how to handle them:

  • First Record: Takes the first matching record (arbitrary sort).
  • Calculate Statistics: Aggregates the matching records (e.g., Sum, Mean, Min, Max).
  • Count Only: Just counts how many matches were found.

One-to-Many: Creates a separate feature in the output for each matching feature in the Join Layer (could duplicate target geometry).

Run​

7
Click Run to execute the join. Result will be added to the map.