topic Re: Find polylines with true curves in ArcMap Questions

Find polylines with true curves

Bud — Tue, 08 Feb 2022 19:29:53 GMT

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.

Re: Find polylines with true curves

DanPatterson — Tue, 08 Feb 2022 23:09:28 GMT

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)

Re: Find polylines with true curves

DanPatterson — Wed, 09 Feb 2022 04:58:40 GMT

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

point counts go up to.

Re: Find polylines with true curves

Bud — Wed, 12 Apr 2023 14:38:30 GMT

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! )

Re: Find polylines with true curves

JamiePetersen — Fri, 10 Feb 2023 20:24:45 GMT

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.

Re: Find polylines with true curves

Nellzor — Wed, 12 Apr 2023 14:00:53 GMT

This worked PERFECTLY. Thank you!

Re: Find polylines with true curves

Bud — Wed, 12 Apr 2023 14:21:07 GMT

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

Re: Find polylines with true curves

Nellzor — Wed, 12 Apr 2023 14:33:40 GMT

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.