Difficulty with Spatial Join & Largest Overlap Relationship

[JuliaPetersen]

Hi,

I'm trying to complete a spatial join between US Postal Service zip codes and US Census ZCTAs. Zip codes and ZCTAs do not perfectly overlap, and many overlap quite a bit. I used the Spatial Join tool and the "Largest Overlap" relationship, and want an output that gives me the zip code and its ZCTA that overlaps it the most. But, when I run it, the consistent result is a mismatch between the Zip Codes and their ZCTAs (I figured this out by visually double checking). Instead, the tool aligns the zip code to a ZCTA that has a very small overlap with the zip code, rather than the zip code with the most overlap (see pics attached).

I've ensured the layers are in the same gdb, the projections are the same, and the geometries are solid. I've tried ESRI's suggested solve for a similar question (Intersect and then Summarize Within). Results remain misaligned. I've successfully used the Largest Overlap relationship for a separate project, but can't get it right for this one. Please help -- thank you!

[Libra66]

I'm having a very similar problem. The largest overlap is actually giving me the smallest overlap as you described. Did you ever get a solution?

[jdu]

Exact same problem for me! Polygons that have 100% overlap are joining correctly, but those that overlap multiple polygons are joining to the target polygon with the smallest - rather than largest - area of overlap. This appears to be a fairly common issue...anyone come up with an idea? Thanks!

[James_Whitacre_PGC]

I am experiencing this same issue. What I have found is that if both/all datasets are the same exact projected coordinate system, I seem to get the correct values. Of course I can't test every feature and it would seem prudent to ensure that the the projected coordinates system is an equal area projection (which I did also) to ensure areas can be accurately compared.

Also, I would add that Esri either need to clarify this in the documentation or enhance the tool code to ensure data with differing coordinates systems are accurately calculating and comparing areas.