ArcGIS Pro Spatial Joint Corrupts shape_length after join

GerryGabrisch

I have a polygon and a line feature class inside of a file geodatabase. Both the feature classes, and the map reference Washington State Plane North NAD83. After doing a spatial join moving attributes from the polygons to the lines I notice the line shape_length attribute had taken the values of the shape_length from the polygons. This is not good because these attributes are supposed to calculate automatically inside a file geodatabase. I am using these shape_lengths and shape_area values in my geoprocessing.

I tried a repair geometry, that did not fix the lengths in the line file. I exported the line feature class to a new line feature class inside the same geodatabase. While this fixed the lengths of the lines this does not give me any confidence in my geoprocessing results.

Has anyone noticed this behavior?

Pro v3.6.4

DanielFox1

Hi @GerryGabrisch

In a file geodatabase, Shape_Length and Shape_Area are system-maintained fields. However, during tools such as Spatial Join, field mapping can sometimes create unexpected output fields when both inputs contain fields with the same names.

For example:

• Target features (lines) have Shape_Length
• Join features (polygons) have Shape_Length
• Spatial Join creates an output schema using field mappings
• The output Shape_Length field may end up populated from the join feature rather than reflecting the line geometry

This is particularly easy to miss if:

• The output was written to a new feature class.
• Custom field mapping was used.
• The resulting field names were automatically reconciled and one field inherited the name you expected.

A useful test

Open the attribute table and compare:

1. Existing Shape_Length
2. Run Calculate Geometry Attributes to a new field such as Line_Length_Check
3. Compare values

If Line_Length_Check contains the expected line lengths while Shape_Length contains polygon perimeter values, then the geometry itself was never corrupted. Only the attribute values were.

What I would do to verify confidence in your results

1. Take the post-Spatial-Join line feature class.
2. Add a new field.
3. Run Calculate Geometry Attributes for line length.
4. Compare against:
   • Current Shape_Length
   • Original line lengths (if available).
5. Run Check Geometry to ensure no geometry issues exist.
6. Review the Spatial Join field map for any inherited polygon Shape_Length field.

If exporting the lines to a new feature class restored the expected lengths exactly, that's actually fairly strong evidence that your line geometry remained correct throughout the process and that the issue was confined to the stored attribute values rather than the geoprocessing results themselves.

Spatial Join (Analysis)—ArcGIS Pro | Documentation

Why Are There Differences in the Shape Area and Shape Length Fields for the Same Feature S

The Shape_Length Field in a Feature Layer’s Attribute Table Displays Inaccurate Values

Add Spatial Join (Data Management Tools) | ArcGIS Pro documentation