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Find polylines with true curves

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02-08-2022 11:29 AM
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by
Honored Contributor

In ArcMap 10.7.1 (Oracle 18c SDE.ST_GEOMETRY):

Using a geoprocessing tool, is there a way to identify polylines that have true curves?

I know there is a hasCurves Geometry property in ArcPy for ArcGIS Pro. But I don't have access to Pro yet. And regardless, I'd rather use a GP tool for this, than ask my users to use a custom script.

Thanks.

7 Replies
MVP Esteemed Contributor

sadly, not, except for converting to a shapefile and compare the geometry lengths

If they differ, then the curve was densified and converted to segments which would have a slightly different length

Geoprocessing considerations for shapefile output—ArcMap | Documentation (arcgis.com)

... sort of retired...
MVP Esteemed Contributor

demonstrating with polygons... The differences for small shapes may not differ much, but they do differ

point counts go up to.

... sort of retired...
by
Honored Contributor

Here's one way of doing it — similar to what Dan showed above.
(it does involve Python, not strictly GP tools)

1. Create a copy of the polyline FC in a FGDB.

2. Optional: Delete unneeded fields using the Delete Field GP tool.

3. Add new fields: Points_Before, Points_After, and Has_Curve.

4. Use Python in the field calculator to populate Points_Before. The Python is: !shape!.pointcount. Source: How To: Count the vertices for line or polygon features in ArcMap

5. Convert the curves to straight segments via using the Densify GP tool. I used the Angle option: 10 degrees.

6. Use Python in the field calculator to populate Points_After.

7. Use Select by Attributes to select lines where Points_Before <> Points_After

8. Use the field calculator to populate the selected records in the Has_Curve field. That field is now a static flag that indicates if a line has a curve or not.

In hindsight, using straight python might have been easier:

Use Python in the Field Calculator on a custom Has_Curves field:

```def has_curves(geom):
geom_orig = geom
geom_densified = geom.densify("ANGLE", 10000, 0.174533)
if geom_orig.pointCount != geom_densified.pointCount:
return "Y"
else:
return None```

`has_curves( !SHAPE! )`

by
New Contributor

This worked PERFECTLY. Thank you!

by
Honored Contributor

Out of curiosity, what technique did you use? The first option I mentioned, or the second "in hindsight" option?

by
New Contributor

The field calculate using Python in ArcGIS Pro 2.9.5. We were going in circles trying to figure out/select which segments were arcs.

Thanks again! Worked as expected.

Occasional Contributor II

First run the Split Line At Vertices.  Then add a field to the result called curveCount.  Then Calculate Geometry to it using the Number of Curves option. The result will be 1 for curve or 0 for not curve.