Join
A fundamental GIS operation that combines attribute data from two tables based on a common field (key). Joins are essential for integrating spatial and non-spatial data, allowing for richer spatial analysis by associating additional attributes with geographic features(inferred from standard GIS usage).
What does the term Join mean?
The process of merging two datasets according to a shared attribute or field is referred to as "joining" in GIS. This function makes it possible to link extra data—typically attribute data—from one table to the features in a different layer.
Important Points:
Using a common key field (such as ID or name)
Uses external attribute data to improve spatial data.
Spatial joins and attribute joins are common types.
Characteristic Join: connections made using a common field
Links based on geographical relationships, such as proximity or containment, are called spatial joins.
In mapping and GIS applications, joins are crucial for performing meaningful spatial analysis and enriching geographic datasets.
Related Keywords
In GIS, combining two datasets based on their physical positions rather than shared characteristics is known as a spatial join. By allocating population data from a polygon layer of districts to points that represent schools inside those districts, for instance, it connects features from one layer to another. This makes geographical analysis possible, including data enrichment or summarization based on intersection, containment, or proximity.
The technique of connecting data from one table to another using a common field, like an ID or name, is known as an attribute join in GIS. This enables better analysis and visualization without changing the underlying datasets by allowing spatial characteristics (such as points, lines, or polygons) to inherit additional non-spatial information. It is frequently used to integrate geographic layers with survey, environmental, or demographic data.
By combining data from two layers according to their spatial relationship—for example, by giving points within them polygon attributes—QGIS's "Join attributes by location" feature creates a new layer with the combined data.
Using a shared field or spatial relationship, the Join Features tool in ArcGIS allows you to merge attributes from one layer (the join layer) to another (the target layer). This enables you to add pertinent information to your data without permanently merging the geometries, such as matching parcels with owner details or points with the nearest polygon properties.