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Select by Location selects parcels that do not overlap with layer used for selection

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02-17-2022 04:09 PM
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MJosefson_SalemMA
New Contributor II

Hi All! I hope someone can suggest some possible culprits to an unexpected behavior I am seeing with a feature layer used by OpenGov for flagging permits for review by different departments depending on whether a property falls within various polygons that would trigger a review. We noticed that a property (37 Broad St) was flagged as historic, but it is not. I downloaded the feature layer into Pro, expecting to see a topology boundary issue between the parcel and the Historic District. I cannot figure it out! Trying my usual tricks for finding gaps and slivers has been fruitless. When I Select by Location from parcels that intersect with Historic Districts, a number of parcels get selected that lie outside those districts. When I Union or Intersect Historic District of interest and parcel(s) of interest, I do not find any overlap polygons generated. What gives? All the layers seem to be in the same projection,  NAD 1983 State Plane MA. Can someone please tell me what's going on? Much appreciated! Here's the feature layer causing trouble.

https://salemma.maps.arcgis.com/home/item.html?id=5b7c4486ba774c7cb0aaa427d588e1f2

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5 Replies
KimGarbade
Regular Contributor

A few ideas... keeping in mind I didn't say good ideas... The parcels might be mutli-part. Less likely, the parcels may be related to another table, or might have been created from a dataset that was. For example parcel data is often linked to CAMA data, a series of relationships could do it. If you select by attribute on 37 Broad St? How many parcels are returned?  Then try selecting by attribute on the RE assigned to that parcel or the owner.  If only one parcel comes back I'm wrong. 

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MJosefson_SalemMA
New Contributor II

I appreciate your brainstorming Kim!

There don't seem to be any CAMA tables attached in the feature layer, and when I select by attribute by Parcel ID, only 37 Broad st is selected. Thank you for the suggestions!

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KimGarbade
Regular Contributor

How far outside the historic district is the parcel that gets selected? 

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MJosefson_SalemMA
New Contributor II

Thanks Kim! They are bordering the Historic District, but when I run a Union or Intersect between the selected parcel and the Historic District, no overlapping sliver is produced.

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KimGarbade
Regular Contributor

I don't want to waste your time. So if you think I'm off base please ignore at will (and even I'm a little iffy on this), but....

Maybe the Union and Intersect tools are honoring setting in your input features (parcels and historic districts) related to X,Y Tolerance and X,Y Resolution and those are creating polygons so small that they are discarded by the tools, but the Select by Location tool is seeing an overlap.  Quick way to test this is to compare the vertices of the 37 Broad St parcel to the historic district parcel's vertices in that area. 

If they are identical and the projection is indeed the same it might just be a bug.  You could try a different "Relationship" in your Select Layer by Location function... maybe "Intersect (DBMS)", but why that would matter I'm not sure.

 

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