7. Select by Location¶

Goal: Use spatial relationships to filter features. The companion of Select by Attributes.

Where to find it¶

Map ribbon → Select by Location, or Geoprocessing tool: Select Layer By Location.

The dialog¶

Input Features:    [the layer to select FROM]
Relationship:      [intersect, within, contains, …]
Selecting Layer:   [the layer that defines the spatial filter]
Search Distance:   [optional — use for "within X meters"]
Selection Type:    [new / add / remove / subset / invert]

Spatial relationships¶

Relationship	Meaning
Intersect	Any overlap (most common)
Within a distance	Within X meters/feet of
Contain	Input contains selecting feature
Within	Input is fully inside selecting feature
Are identical to	Exact geometric match
Are crossed by	Line crosses through
Touch the boundary of	Share a boundary, no interior overlap
Have their center in	Polygon centroid in selecting feature
Share a line segment with	Topologically connected

Classic patterns¶

"Schools within 1 mile of a major road"¶

Input Features:  Schools
Relationship:    Within a distance
Selecting Layer: Major Roads
Search Distance: 1 Miles

"Census tracts that intersect the floodplain"¶

Input Features:  Census Tracts
Relationship:    Intersect
Selecting Layer: Floodplain

"Parcels fully inside Fulton County"¶

Input Features:  Parcels
Relationship:    Within
Selecting Layer: Fulton County

"Cities that contain at least one airport"¶

Input Features:  Cities
Relationship:    Contain
Selecting Layer: Airports

Combining attribute + location¶

Real workflows combine both. Two patterns:

A. Sequential¶

Select by Attributes to filter the input first.
Select by Location with Subset selection.

B. Within a query¶

For most cases, run them as separate steps and inspect the count after each. Easier to debug.

Coordinate system reminder¶

Distance-based selections use map units. If your layer is in WGS84 (lat/long), "1 mile" is meaningless — Pro will warn you. Project to a CRS in feet or meters first.

→ See Coordinate Systems & Projections.

Convert selection to layer¶

After any selection, right-click → Selection → Convert Selection To Layer. Now you have a separate, persistent layer that's only the selected features.

Selection vs Spatial Join¶

Selection	Spatial Join
Highlights features	Creates a new feature class
Doesn't transfer attributes	Combines attributes from both layers
Use to filter	Use to attach data

→ See Spatial Join.

Practice¶

Multi-step location query

Add: streets, hospitals, county boundary.
Project all to State Plane.
Select streets Within a distance of 500 m of hospitals.
Subset that selection to streets that Are within the county boundary.
Convert selection to layer → label as "Hospital access streets, in-county".

→ Next: Joins & Relates.