ArcMap

Smooth Line

Summary

Smooths sharp angles in lines to improve aesthetic or cartographic quality.

Illustration

Smooth Line illustration

Usage

  • There are two smoothing methods to choose from:

    • The Polynomial Approximation with Exponential Kernel (PAEK) method (PAEK in Python) smooths lines based on a smoothing tolerance. Each smoothed line may have more vertices than its source line. The Smoothing Tolerance parameter controls the length of a "moving" path used in calculating the new vertices. The shorter the length the more detail that will be preserved and the longer the processing time.
    • The Bezier interpolation method (BEZIER_INTERPOLATION in Python) smooths lines without using a tolerance by creating Bezier curves to match the input lines. If the output is a shapefile, the Bezier curves will be approximated, since true Bezier curves cannot be storied in shapefiles.

  • Smoothing may introduce topological errors such as line crossings. Use the Flag errors option (FLAG_ERRORS in Python) in the Handle Topological Errors parameter to identify these errors. Two fields will be added—InLine_FID and SmoLnFlag—to contain input feature IDs and topological errors. Values of 1 in the SmoLnFlag field indicate a topology error; 0 (zero) indicates no error. The InLineFID field links the output lines to their input lines. The Flag errors option cannot be used within an edit session.

  • Invalid (self-intersecting) geometry may be created during the smoothing process and will be repaired but not improved. For example, if a line self-crosses it will become a multipart line but will still appear self-crossing.

Syntax

SmoothLine_cartography (in_features, out_feature_class, algorithm, tolerance, {endpoint_option}, {error_option})
ParameterExplanationData Type
in_features

The line features to be smoothed.

Feature Layer
out_feature_class

The output feature class to be created.

Feature Class
algorithm

Specifies the smoothing algorithm.

  • PAEK —Acronym for Polynomial Approximation with Exponential Kernel. It calculates a smoothed line that will not pass through the input line vertices. This is the default.
  • BEZIER_INTERPOLATION —Fits Bezier curves between vertices. The resulting line passes through the vertices of the input line. This algorithm does not require a tolerance. Bezier curves will be approximated in shapefile output.
String
tolerance

Sets a tolerance used by the PAEK algorithm. A tolerance must be specified, and it must be greater than zero. You can choose a preferred unit; the default is the feature unit. You must enter a 0 as a placeholder when using the BEZIER_INTERPOLATION smoothing algorithm.

Linear Unit
endpoint_option
(Optional)

Specifies whether to preserve the endpoints for closed lines. This option works with the PAEK algorithm only.

  • FIXED_CLOSED_ENDPOINT —Preserves the endpoint of a closed line. This is the default.
  • NO_FIXED —Smooths through the endpoint of a closed line.
Boolean
error_option
(Optional)

Specifies how the topological errors (possibly introduced in the process, such as line crossing) will be handled.

  • NO_CHECK —Specifies not to check for topological errors. This is the default.
  • FLAG_ERRORS —Specifies to flag topological errors, if any are found.
String

Code sample

SmoothLine example (Python window)

The following Python window script demonstrates how to use the SmoothLine tool in immediate mode.

import arcpy
import arcpy.cartography as CA
arcpy.env.workspace = "C:/data"
CA.SmoothLine("contours.shp", "C:/output/output.gdb/smoothed_contours", "PAEK", 100)
SmoothLine example 2 (stand-alone script)

The following stand-alone script demonstrates how to use the SmoothLine tool.

# Name: SmoothLine_Example2.py
# Description: Simplify and then Smooth coastlines
 
# Import system modules
import arcpy
import arcpy.cartography as CA
 
# Set environment settings
arcpy.env.workspace = "C:/data/Portland.gdb/Hydrography"
 
# Set local variables
inCoastlineFeatures = "coastlines"
simplifiedFeatures = "C:/data/PortlandOutput.gdb/coastlines_simplified"
smoothedFeatures = "C:/data/PortlandOutput.gdb/coastlines_smoothed"

# Simplify coastlines.
CA.SimplifyLine(inCoastlineFeatures, simplifiedFeatures, "POINT_REMOVE", 50, "RESOLVE_ERRORS", "KEEP_COLLAPSED_POINTS", "CHECK")
 
# Smooth coastlines.
CA.SmoothLine(simplifiedFeatures, smoothedFeatures, "PAEK", 100, "", "FLAG_ERRORS")

Environments

Licensing information

  • ArcGIS Desktop Basic: No
  • ArcGIS Desktop Standard: Yes
  • ArcGIS Desktop Advanced: Yes

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