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Match by "Largest Overlap" for Select Layer by Location

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2
01-02-2024 06:52 AM
Status: Needs Clarification
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MErikReedAugusta
by
Occasional Contributor III

The GP Analysis Tool, Spatial Join has a Match Option parameter of "Largest Overlap" that doesn't appear in the otherwise-identical list of Select Layer By Location.

It'd be nice if I could use that new toy across all other contexts where I'm doing things between two datasets based on their locations.

Right now, the selection-only operation seems to require the use of intermediate datasets, which is a bit undesirable—especially for the option that I'm more likely to reach for when I don't want other datasets being created.

2 Comments
DrewFlater
by Esri Regular Contributor
a month ago
Status changed to: Needs Clarification

The Largest Overlap option was added to Spatial Join only, as Spatial Join does a one by one operation for each target feature, where each target feature is examined to determine if any join features have a spatial relationship with that target feature. If many join features have the spatial relationship with the one target feature, Largest Overlap joins the join feature that has the largest overlap to the target feature. 

Thinking about Select Layer By Location is different. Any input feature gets selected if it has the spatial relationship with any selecting feature. There is no handling about what if an input feature overlaps multiple selecting features, or if multiple input features overlap the same selecting feature.

Imagine this case, where a green feature overlaps a big orange feature (id=1) and a small orange feature (id=2).

DrewFlater_0-1718742476405.png

 

  • If the green feature is the input and the orange features are the selecting feature, a Largest Overlap relationship doesn't make sense - the green feature is going to get selected because it overlaps any orange features.
  • If the orange features are the input features and the green feature is the selecting feature, first orange 1 is evaluated for a spatial relationship with green (it overlaps) then orange 2 is evaluate for a spatial relationship with green (it overlaps) -- so both orange would get selected. There isn't a mode of select layer by location that would unselect orange 2 because orange 1 has a larger overlap with a single green feature. 

If you can graphically describe what your expectation is between two feature layers and how a selection could be performed based on a Largest Overlap relationship, please share the details to get this issue reopened for votes/consideration.