Copy Traversed Source Features (Network Analyst)

License Level:BasicStandardAdvanced

Summary

Creates two feature classes and a table, which together contain information about the edges, junctions, and turns that are traversed while solving a network analysis layer.

Learn about the output from Copy Traversed Source Features

Usage

Syntax

CopyTraversedSourceFeatures_na (input_network_analysis_layer, output_location, edge_feature_class_name, junction_feature_class_name, turn_table_name)
ParameterExplanationData Type
input_network_analysis_layer

The network analysis layer from which traversed source features will be copied. If the network analysis layer does not have a valid result, the layer will be solved to produce one.

Network Analyst Layer
output_location

The workspace where the output table and two feature classes will be saved.

Workspace; Feature Dataset
edge_feature_class_name

The name of the feature class that will contain information about the traversed edge source features. If the solved network analysis layer doesn't traverse any edge features, an empty feature class is created.

String
junction_feature_class_name

The name of the feature class that will contain information about the traversed junction source features, including system junctions and relevant points from the input network analysis layer. If the solved network analysis layer doesn't traverse any junctions, an empty feature class is created.

String
turn_table_name

The name of the table that will contain information about the traversed global turns and turn features that scale cost for the underlying edges. If the solved network analysis layer doesn't traverse any turns, an empty table is created. Since restricted turns are never traversed, they are never included in the output.

String

Code Sample

CopyTraversedSourceFeatures example 1 (Python Window)

The following Python window script demonstrates how to use the CopyTraversedSourceFeatures tool to write the traversed edges, junctions, and turns from a Route network analysis layer to feature classes and table in an in-memory workspace.

arcpy.na.CopyTraversedSourceFeatures("Route", "C:/Data/Output.gdb",
                                     "TraversedEdges",
                                     "TraversedJunctions",
                                     "TraversedTurns")
CopyTraversedSourceFeatures example 2 (workflow)

The following stand-alone Python script demonstrates how CopyTraversedSourceFeatures can be used to find the streets that are common to the routes from census tract centroids to the closest fire station. These results help identify which streets are most frequently used emergencies.

# Name: CopyTraversedSourceFeatures_ex02.py
# Description: The scenario shows how to find the streets that are common to the
#              routes between the closest fire station and the census tract
#              centroids. These streets can be used to identify critical points
#              in case of an emergency. 
# Requirements: Network Analyst Extension 

#Import system modules
import os
import arcpy
from arcpy import env

try:
    #Check out the Network Analyst extension license
    arcpy.CheckOutExtension("Network")

    #Set environment settings
    env.workspace = "C:/data/SanFrancisco.gdb"
    env.overwriteOutput = True
    
    #Set local variables
    inNetworkDataset = "Transportation/Streets_ND"
    outNALayerName = "EmergencyRoutes"
    impedanceAttribute = "TravelTime"
    inFacilities = "Analysis/FireStations"
    inIncidents = "Analysis/TractCentroids"
    edgeFrequency = "in_memory/EdgeFrequency"
    outLayerFile = "C:/data/output" + "/" + outNALayerName + ".lyr"
    outFeatures = "CriticalStreets"
    
    #Create a new closest facility analysis layer. For this scenario, the default 
    #value for all the remaining parameters statisfies the analysis requirements
    outNALayer = arcpy.na.MakeClosestFacilityLayer(inNetworkDataset, outNALayerName,
                                                   impedanceAttribute, "TRAVEL_FROM")
    
    #Get the layer object from the result object. The closest facility layer can 
    #now be referenced using the layer object.
    outNALayer = outNALayer.getOutput(0)
    
    #Get the names of all the sublayers within the closest facility layer.
    subLayerNames = arcpy.na.GetNAClassNames(outNALayer)
    #Stores the layer names that we will use later
    facilitiesLayerName = subLayerNames["Facilities"]
    incidentsLayerName = subLayerNames["Incidents"]
    
    #Load fire station features as facilities and ensure that they are not
    #located on restricted portions of the network. Use default field mappings
    #and search tolerance
    arcpy.na.AddLocations(outNALayer,facilitiesLayerName,inFacilities,"", "",
                          exclude_restricted_elements = "EXCLUDE")
    
    #Load tract centroids as incidents and ensure that they are not located on
    #restricted portions of the network. Map the ID field from Tract Centroids
    #as the name for incidents using field mappings
    fieldMappings = arcpy.na.NAClassFieldMappings(outNALayer, incidentsLayerName)
    fieldMappings['Name'].mappedFieldName = "ID"
    arcpy.na.AddLocations(outNALayer,incidentsLayerName, inIncidents,
                          fieldMappings,"", exclude_restricted_elements = "EXCLUDE")
    
    #Solve the closest facility layer and copy the travered source features to a
    #temporary in-memory workspace. Use default names for the output feature
    #classes and table. Get only the first output which are the edges traversed.
    traversedEdges = arcpy.na.CopyTraversedSourceFeatures(outNALayer,
                                                          "in_memory").getOutput(0)
    
    #Calculate the frequency of SourceOID in the traversed edges
    arcpy.analysis.Frequency(traversedEdges, edgeFrequency,
                             ["SourceOID", "SourceName"])
    
    #Get the full path to the streets feature class by describing the network
    #dataset referenced by the network analysis layer. 
    network = arcpy.Describe(outNALayer.dataSource)
    edgeSources = network.edgeSources
    for es in edgeSources:
        if es.name.lower() == "streets":
            streetsSource = os.path.join(os.path.dirname(network.catalogPath),
                                         es.name)
            break
    else:
        raise Exception("Failed to detrmine the path for the streets feature class")
    
    #Join the frequency field to the streets feature class. In order to speed up
    #the join select the streets that share a line segment with traversed streets.
    streetsLayer = "StreetsLayer"
    arcpy.management.MakeFeatureLayer(streetsSource,streetsLayer)
    arcpy.management.SelectLayerByLocation(streetsLayer, "SHARE_A_LINE_SEGMENT_WITH",
                                           traversedEdges)
    arcpy.management.JoinField(streetsLayer, "ObjectID", edgeFrequency,
                               "SourceOID", "FREQUENCY")
    
    #Copy the streets that have a frequency value to a new feature class.
    arcpy.management.SelectLayerByAttribute(streetsLayer, "SUBSET_SELECTION",
                                            "FREQUENCY IS NOT NULL")
    arcpy.management.CopyFeatures(streetsLayer,outFeatures)
    
    #Delete the Frequency field from the streets feature class
    arcpy.management.DeleteField(streetsLayer, "FREQUENCY")

    #Save the solved na layer as a layer file on disk with relative paths
    arcpy.management.SaveToLayerFile(outNALayer,outLayerFile,"RELATIVE")
    
    print "Script completed successfully"
    
except Exception as e:
    # If an error occurred, print line number and error message
    import traceback, sys
    tb = sys.exc_info()[2]
    print "An error occured on line %i" % tb.tb_lineno
    print str(e)

Environments

Related Topics

Licensing Information

ArcGIS for Desktop Basic: Requires Network Analyst
ArcGIS for Desktop Standard: Requires Network Analyst
ArcGIS for Desktop Advanced: Requires Network Analyst
1/20/2015