1. GIS Lecture: Spatial Joins

2. Spatial Joins

3. Spatial join example
You have census block group centroid points with housing fuel data
You want to know housing fuel use for whole neighborhoods
But there are no attributes in common
Spatial join is needed

4. Spatial joins Points to polygons
Spatially joins points (block centroids) within polygons (neighborhoods)
Joins using “shape” (not an attribute field)

5. Spatial joins
Right-click the polygon layer (neighborhoods)

6. Join result
New polygon feature

7. Join result Count – how many points are in each neighborhood
Sums – adds up the field values within each neighborhood

8. Count result
Number of points in each polygon

9. Sum result One neighborhood example Central business district
4 block groups
Housing units with electricity fuel from block group centroids field [H040004] ( )
Sum = 799

10. Choropleth map result (sum)

11. Spatial Joins