0

I have a boundary (clipper) and street data (lines, clipee). I calculate the sum of the street length within the boundary for communities.

From a performance perspective this is faster to do over many communities at once, using an intersect, as opposed to select communities and clip individually. However, to check the result, I clipped them individually and compared the result. The results differ in every community. I suspect this being some tolerance/precision setting, but cannot get at a different result manually setting tolerance. There is a visual offset between the clipped line and the result of the intersection.

Is there any other difference in handling of the geometries between these 2 tools that causes this?

ArcGIS Pro 2.9.3

enter image description here

Red line from intersection, blue line from clip. Light blue is the clipping polygon. Distance not really measurable in ArcGIS Pro, has to be below 1mm I think. Since the boundary sometimes goes along the direction of the street, the differences amount to several meters overall.

Improve this question
8
  • 1
    Are both your layer in the same CRS ? if not the tools may behave differently to reproject one or both layer
    – J.R
    Jun 16, 2022 at 13:36
  • Can you share an example?
    – Binx
    Jun 16, 2022 at 14:08
  • Product and version? Although arcgis-pro was tagged, it is good to state it in the question along with version
    – bixb0012
    Jun 16, 2022 at 14:10
  • I assume you have checked the geometry of both layers, but you want to make sure the communities polygons have no overlapping polys prior to the intersect, and/or you might want to planarize your lines after one to get rid of line overlaps before recalculating your lengths. You might want show what is happening visually. How much of a difference are you getting; at what scale are you seeing a "visual offset"? When you say offset, do you mean one line is longer than the other or the lines have shifted relative to each other.
    – John
    Jun 16, 2022 at 14:36
  • 3
    It looks like your municipal polygon boundaries that run along streets are not coincident with the streets. Vertices might be offset and/or there may be many more vertices in one compared to the other. If you 1:) put them in a topology and validate it, or 2:) you run the Integrate tool on them (use copies, the tool changes inputs), or 3:) snap one layer to the other (you may need to densify one first), and then run your Intersect and Clip tools what do you get? Where streets cross boundaries I could envision a difference as Intersect would preserve line topology; clip results are separate.
    – John
    Jun 16, 2022 at 16:35

1 Answer 1

Reset to default
0

I think this explains the select behavior really well and illustrates why the select behavior doesn't match with the clip behavior, but it doesn't explain why there is a difference.

https://pro.arcgis.com/en/pro-app/latest/tool-reference/data-management/select-by-location-graphical-examples.htm

Improve this answer

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.