Simplify Line (Cartography)

Summary

Simplifies lines by removing extraneous bends while preserving essential shape.

Learn more about how Simplify Line works

Illustration

Usage

• There are two simplification methods:

  • The point remove method is the faster of the two processes. It removes redundant vertices. Use this method for data compression or more coarser simplification, especially when the data is well-known. The angularity (sharp corners) of the resulting line will increase significantly as the tolerance increases, so the line may become less aesthetically pleasing.
  • The bend simplify method is slower but typically produces results that are more faithful to the original and more aesthetically pleasing. It operates by eliminating insignificant bends along lines. Use this method for less, more refined simplification.

• The simplification tolerance value determines the degree of simplification. Set the tolerance equal to or greater than the minimum allowable spacing between graphic elements. Using the same tolerance, point remove produces rougher and more simplified results than bend simplify.

• The tool produces two output feature classes: a line feature class to store the simplified lines and a point feature class to store points that represent any lines that were collapsed to zero-length. The point output name and location is automatically derived from the output line name with a _Pnt suffix. The line output will contain all the input fields; the point output will not contain any of the input fields.

• There are options for handling topological errors in the output:

  • The Check for topological errors parameter identifies topological errors introduced by the simplification process. When the option is checked, the Resolve topological errors parameter will also be enabled. Processing is faster without a topology check, but you should use this parameter if you do not have confidence in the topological accuracy of the data.
  • The line output will contain two new fields to indicate whether or not a feature has a topological error. InLine_FID and SimLnFlag contain the input feature IDs and topological errors, respectively. A value of 1 indicates an error was introduced, while 0 (zero) indicates that no errors were introduced.
  • The flag values will remain in place after a topological error has been resolved. Use the SimLnFlag field to examine features that have topological errors.

• The Check for topological errors and Resolve topological errors parameters cannot be used within an edit session. Disable the Check for topological errors parameter in order to run the tool within an edit session.

Syntax

SimplifyLine_cartography (in_features, out_feature_class, algorithm, tolerance, {error_resolving_option}, {collapsed_point_option}, {error_checking_option})

Parameter	Explanation	Data Type
in_features	The line features to be simplified.	Feature Layer
out_feature_class	The output line feature class to be created.	Feature Class
algorithm	Specifies the line simplification algorithm. POINT_REMOVE —Keeps the so-called critical points that depict the essential shape of a line and removes all other points. This is the default. BEND_SIMPLIFY —Keeps the main shape of a line and removes extraneous bends.	String
tolerance	The tolerance that determines the degree of simplification. A tolerance must be specified, and it must be greater than zero. You can choose a preferred unit; the default is the feature unit. For POINT_REMOVE algorithm, the tolerance you specify is the maximum allowable offset of each vertex from its original location. This value may be reduced locally in some areas when the option is used to resolve topological errors. For BEND_SIMPLIFY algorithm, the tolerance you specify is the length of the reference bend baseline.	Linear unit
error_resolving_option (Optional)	Specifies how the topological errors (possibly introduced in the process, including line crossing, line overlapping, and collapsed zero-length lines) will be handled. This parameter will be in effect when the error_checking_option is CHECK (the default). FLAG_ERRORS —Specifies to flag topological errors, if any are found. This is the default. RESOLVE_ERRORS —Specifies to resolve topological errors, if any are found.	Boolean
collapsed_point_option (Optional)	Specifies whether to keep collapsed zero-length lines as points if any are found in the process. This option applies only when NO_CHECK is specified or when both FLAG_ERRORS and CHECK options are specified. KEEP_COLLAPSED_POINTS —Specifies to keep the collapsed zero-length lines as points. The endpoints of the collapsed lines will be stored in a point feature class at the output feature class location, taking the name of the output feature class plus a suffix _Pnt. This is the default. NO_KEEP —Specifies not to keep the collapsed zero-length lines as points even if they are found in the process; therefore, the point feature class will be empty.	Boolean
error_checking_option (Optional)	Specifies how the topological errors (possibly introduced in the process, including line crossing, line overlapping, and collapsed zero-length lines) will be handled. CHECK —Specifies to check for topological errors and enables the error_resolving_option parameter. This is the default. NO_CHECK —Specifies not to check for topological errors and disables the error_resolving_option parameter.	Boolean

Code Sample

SimplifyLine example (Python window)

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

import arcpy
from arcpy import env
import arcpy.cartography as CA
env.workspace = "C:/data"
CA.SimplifyLine("roads.shp", "C:/output/output.gdb/simplified_roads", "POINT_REMOVE", 20)

SimplifyLine example 2 (stand-alone script)

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

# Name: SimplifyLine_Example2.py
# Description: Simplify line features from two feature classes, rivers and coastlines,
# while maintaining their connections

 
# Import system modules
import arcpy
from arcpy import env
import arcpy.management as DM
import arcpy.cartography as CA
 
# Set environment settings
env.workspace = "C:/data/Portland.gdb/Hydrography"
 
# Set local variables
inRiverFeatures = "rivers"
inCoastlineFeatures = "coastlines"

mergedFeatures = "C:/data/PortlandOutput.gdb/merged_lines"
simplifiedFeatures = "C:/data/PortlandOutput.gdb/merged_lines_simplified"
tempLayer = "tempLyr"

outRiverFeatureClass = "C:/data/PortlandOutput.gdb/rivers_final"
outCoastlineFeatureClass = "C:/data/PortlandOutput.gdb/coastlines_final"

# Merge rivers and coastlines into one feature class, assuming that they have 
#  a common f-code field with value 40 for rivers and 80 for coastlines.
DM.Merge(inRiverFeatures, inCoastlineFeatures, mergedFeatures)
# Simplify all lines.
CA.SimplifyLine(mergedFeatures, simplifiedFeatures, "BEND_SIMPLIFY", 100, "RESOLVE_ERRORS", "KEEP_COLLAPSED_POINTS", "CHECK")
 
# Select rivers and coastlines by their f-code values and put them in separate feature classes.
DM.MakeFeatureLayer(simplifiedFeatures, tempLayer, "f-code = 40")
DM.CopyFeatures(tempLayer, outRiverFeatureClass)

DM.MakeFeatureLayer(simplifiedFeatures, tempLayer, "f-code = 80")
DM.CopyFeatures(tempLayer, outCoastlineFeatureClass)

Environments

Current Workspace, Default Output Z Value, Output M Domain, Output XY Domain, Output Coordinate System, Extent, Output has M values, Output has Z values, Scratch Workspace, XY Tolerance

Licensing Information

ArcView: No

ArcEditor: Yes

ArcInfo: Yes