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Trace (Trace Network)

In this topic

  1. Summary
  2. Usage
  3. Syntax
  4. Code sample
  5. Environments
  6. Licensing information

Summary

Returns selected features in a trace network based on connectivity or traversability from the specified starting points.

The trace capabilities of the trace network allow you to analyze paths in your network. Traversability refers to paths established by connected features that also meet configuration requirements.

By default, trace results are returned as a selection and include the entire line feature. To return partial feature results, set the Result Types parameter to Aggregate Geometry. When a starting point or barrier is placed on a junction with midspan connectivity, trace results will return partial elements of the edge feature. When a barrier is placed along an edge, trace results can be stopped at the nearest junction with midspan connectivity. The resulting selection set or output feature class generated by the trace can then be propagated to another map, propagated to a diagram view of the network, or used as input to another tool or trace.

Learn more about tracing a trace network

Usage

  • The network topology must be enabled.

  • When working with an enterprise geodatabase, an input trace network must be from a feature service; a trace network from a database connection is not supported.

  • Because the Trace tool relies on the network topology, the trace results are not guaranteed to be accurate if dirty areas exist in the trace extent. The network topology for the area to be traced must be validated to reflect the most recent edits or updates to the network.

  • When working with network attributes assigned to a date field for condition barriers, function barriers, functions, and output conditions, the date value should be formatted as yyyy-mm-dd hh:mm:ss, for example, 2020-10-12 18:45:31.

Syntax

arcpy.tn.Trace(in_trace_network, trace_type, starting_points, {barriers}, {path_direction}, {shortest_path_network_attribute_name}, {include_barriers}, {validate_consistency}, {ignore_barriers_at_starting_points}, {allow_indeterminate_flow}, {condition_barriers}, {function_barriers}, {traversability_scope}, {functions}, {output_conditions}, {result_types}, selection_type, {clear_all_previous_trace_results}, {trace_name}, {aggregated_points}, {aggregated_lines}, {out_network_layer}, {use_trace_config}, {trace_config_name})
ParameterExplanationData Type
in_trace_network

The trace network on which the trace will be run. When working with an enterprise geodatabase, an input trace network must be from a feature service; a trace network from a database connection is not supported.

Trace Network; Trace Network Layer
trace_type

Species the type of trace to execute.

  • CONNECTED —A connected trace that begins at one or more starting points and spans outward along connected features will be used.
  • UPSTREAM —An upstream trace that discovers features upstream from a location in the network will be used. This type of trace requires the flow direction to be set.
  • DOWNSTREAM —A downstream trace that discovers features downstream from a location in the network will be used. This type of trace requires the flow direction to be set.
  • SHORTEST_PATH —A shortest path trace that finds the shortest path between two starting points in the network regardless of flow direction will be used. The cost of traversing the path is determined based on the network attribute set for the shortest_path_network_attribute_name parameter.
String
starting_points

A feature layer created using the Starting Points tool in the Trace Locations pane, or a table or feature class containing one or more records that represent the starting points of the trace. The TN_Temp_Starting_Points feature class is used by default and is generated in the default geodatabase of the project when you create starting points using the Starting Points tool in the Trace Locations pane.

Feature Layer; Table View
barriers
(Optional)

A table or feature class containing one or more features that represent the barriers of the trace that prevent the trace from traversing beyond that point. The TN_Temp_Barriers feature class is used by default and is generated in the default geodatabase of the project when you create barriers using the Barriers tool in the Trace Locations pane.

Feature Layer; Table View
path_direction
(Optional)

Specifies the direction of the trace path. The cost of traversing the path is determined by the shortest_path_network_attribute_name parameter value. This parameter is only honored when running a SHORTEST_PATH trace type.

  • NO_DIRECTION —The path between the two starting points, regardless of the direction of flow, will be used. This is the default.
  • PATH_UPSTREAM —The upstream path between the two starting points will be used.
  • PATH_DOWNSTREAM —The downstream path between the two starting points will be used.
String
shortest_path_network_attribute_name
(Optional)

The name of the network attribute used to calculate the path. When running a shortest path trace type, the shortest path is calculated using a numeric network attribute such as shape length. Cost and distance based paths can both be achieved. This parameter is required when running a shortest path trace.

String
include_barriers
(Optional)

Specifies whether the traversability barrier features will be included in the trace results.

  • INCLUDE_BARRIERS —Traversability barrier features will be included in the trace results. This is the default.
  • EXCLUDE_BARRIERS —Traversability barrier features will not be included in the trace results.
Boolean
validate_consistency
(Optional)

Specifies whether an error will be returned if dirty areas are encountered in any of the traversed features. This is the only way to guarantee a trace is passing through features with consistent status in the network. To remove dirty areas, validate the network topology.

  • VALIDATE_CONSISTENCY —The trace will return an error if dirty areas are encountered in any of the traversed features. This is the default.
  • DO_NOT_VALIDATE_CONSISTENCY —The trace will return results regardless of whether dirty areas are encountered in any of the traversed features.
Boolean
ignore_barriers_at_starting_points
(Optional)

Specifies whether barriers in the trace configuration will be ignored for starting points.

  • IGNORE_BARRIERS_AT_STARTING_POINTS —Barriers at starting points will be ignored in the trace.
  • DO_NOT_IGNORE_BARRIERS_AT_STARTING_POINTS —Barriers at starting points will not be ignored in the trace. This is the default.
Boolean
allow_indeterminate_flow
(Optional)

Specifies whether features that have indeterminate or uninitialized flow will be traced. This parameter is only honored when running an upstream or downstream trace.

  • TRACE_INDETERMINATE_FLOW —Features that have indeterminate or uninitialized flow direction will be traced.
  • IGNORE_INDETERMINATE_FLOW —Features that have indeterminate or uninitialized flow direction will not be traced. This is the default.
Boolean
condition_barriers
[Name, Operator, Type, Value, Combine Using,...]
(Optional)

Sets a traversability barrier condition on features based on a comparison to a network attribute. A condition barrier uses a network attribute, an operator and a type, and an attribute value. For example, stop a trace when a feature has the Code attribute equal to the specific value of ArtificialPath. When a feature meets this condition, the trace stops. If you're using more than one attribute, you can use the Combine Using component to define an And or an Or condition.

Condition barrier components are as follows:

  • Name—Filter by any network attribute defined in the system.
  • Operator—Choose from a number of different operators.
  • Type—Choose a specific value or network attribute from the value specified in the Name component.
  • Value—Provide a specific value for the input attribute type that would cause termination based on the operator value.
  • Combine Using—Set this value if you have multiple attributes to add. You can combine them using an And or an Or condition.

Operator components are as follows:

  • IS_EQUAL_TO —The attribute is equal to the value.
  • DOES_NOT_EQUAL —The attribute is not equal to the value.
  • IS_GREATER_THAN —The attribute is greater than the value.
  • IS_GREATER_THAN_OR_EQUAL_TO —The attribute is greater than or equal to the value.
  • IS_LESS_THAN —The attribute is less than the value.
  • IS_LESS_THAN_OR_EQUAL_TO —The attribute is less than or equal to the value.

Type components are as follows:

  • SPECIFIC_VALUE —Filter by a specific value.
  • NETWORK_ATTRIBUTE —Filter by a network attribute.

Combine Using component are as follows:

  • AND —Combine the condition barriers.
  • OR —Use or if either condition barrier is met.
Value Table
function_barriers
[Function, Attribute, Operator, Value, Use Local Values,...]
(Optional)

Sets a traversability barrier on features based on a function. Function barriers can be used, for example, to restrict how far the trace travels from the starting point or to set a maximum value to stop a trace. For example, the length of each line traveled is added to the total distance traveled so far. When the total length traveled reaches the value specified, the trace stops.

Function barrier components are as follows:

  • Function—Choose from a number of calculation functions.
  • Attribute—Filter by any network attribute defined in the system.
  • Operator—Choose from a number of operators.
  • Value—Provide a specific value for the input attribute type that, if discovered, will cause the termination.
  • Use Local Values—Calculate values in each direction as opposed to an overall global value. For example, a function barrier calculates the sum of shape length in which the trace terminates if the value is greater than or equal to 4. In the global case, after you have traversed two edges with a value of 2, you have already reached a shape length sum of 4, so the trace stops. If local values are used, the local values along each path change, and the trace continues.

Function components are as follows:

  • AVERAGE —The average of the input values.
  • COUNT —The number of features.
  • MAX —The maximum of the input values.
  • MIN —The minimum of the input values.
  • ADD —Add the values.
  • SUBTRACT —Subtract the values.

Operator components are as follows:

  • IS_EQUAL_TO —The attribute is equal to the value.
  • DOES_NOT_EQUAL —The attribute is not equal to the value.
  • IS_GREATER_THAN —The attribute is greater than the value.
  • IS_GREATER_THAN_OR_EQUAL_TO —The attribute is greater than or equal to the value.
  • IS_LESS_THAN —The attribute is less than the value.
  • IS_LESS_THAN —The attribute is less than the value.

Use Local Values components are as follows:

  • TRUE —Use local values.
  • FALSE —Use global values. This is the default.
Value Table
traversability_scope
(Optional)

Specifies the type of traversability to enforce. Traversability scope determines whether traversability is enforced at junctions, edges, or both. For example, in a network of recreational trails, if a condition barrier is defined to stop the trace if the path type is gravel and traversability scope is set to junctions only, the trace will not stop even if it encounters a gravel path, because the path type is only applicable to edges. In other words, this parameter indicates to the trace whether to ignore junctions, ignore edges, or include both junctions and edges in the trace.

  • BOTH_JUNCTIONS_AND_EDGES —Traversability will be applied to both junctions and edges. This is the default.
  • JUNCTIONS_ONLY —Traversability will be applied to junctions only.
  • EDGES_ONLY —Traversability will be applied to edges only.
String
functions
[[Function, Attribute, Filter Name, Filter Operator, Filter Type, Filter Value],...]
(Optional)

Applies a calculation function to the trace results.

Functions components are as follows:

  • Function—Choose from a number of calculation functions.
  • Attribute—Filter by any network attribute defined in the system.
  • Filter Name—Filter the function results by attribute name.
  • Filter Operator—Choose from a number of operators.
  • Filter Type—Choose from a number of filter types.
  • Filter Value—Provide a specific value for the input filter attribute.

Function component options are as follows:

  • AVERAGE —The average of the input values.
  • COUNT —The number of features.
  • MAX —The maximum of the input values.
  • MIN —The minimum of the input values.
  • ADD —The sum of the values.
  • SUBTRACT —The difference between the values.

For example, you have a starting point feature with a value of 20. The next feature has a value of 30. If you are using the MIN function, the result is 20. MAX is 30, ADD is 50, AVERAGE is 25, COUNT is 2, and SUBTRACT is -10.

Filter Operator component options are as follows:

  • IS_EQUAL_TO —The attribute is equal to the value.
  • DOES_NOT_EQUAL —The attribute is not equal to the value.
  • IS_GREATER_THAN —The attribute is greater than the value.
  • IS_GREATER_THAN_OR_EQUAL_TO —The attribute is greater than or equal to the value.
  • IS_LESS_THAN —The attribute is less than the value.
  • IS_LESS_THAN —The attribute is less than the value.

Filter Type component options are as follows:

  • SPECIFIC_VALUE —Filter by a specific value.
  • NETWORK_ATTRIBUTE —Filter by a network attribute.
Value Table
output_conditions
[[Name, Operator, Type, Value, Combine Using],...]
(Optional)

The types of features that will be returned based on a network attribute. For example, in a trace configured to filter out everything but Tap features, any traced features that do not have the Tap attribute assigned to them are not included in the results. Any traced features that do are returned in the result selection set. If using more than one attribute, you can use the Combine Using option to define an And or an Or condition.

Output conditions components are as follows:

  • Name—Filter by any network attribute defined in the system.
  • Operator—Choose from a number of operators.
  • Type—Choose a specific value or network attribute from the value =specified in the Name component.
  • Value—Provide a specific value of the input attribute type that would cause termination based on the operator value.
  • Combine Using—Set this value if you have multiple attributes to add. You can combine them using an And or an Or condition.

Operator component options are as follows:

  • IS_EQUAL_TO —The attribute is equal to the value.
  • DOES_NOT_EQUAL —The attribute is not equal to the value.
  • IS_GREATER_THAN —The attribute is greater than the value.
  • IS_GREATER_THAN_OR_EQUAL_TO —The attribute is greater than or equal to the value.
  • IS_LESS_THAN —The attribute is less than the value.
  • IS_LESS_THAN —The attribute is less than the value.

Type component options are as follows:

  • SPECIFIC_VALUE —Filter by a specific value.
  • NETWORK_ATTRIBUTE —Filter by a network attribute.

Combine Using component options are as follows:

  • AND —Combine the conditions.
  • OR —Use or if either condition is met.
Value Table
result_types
[result_types,...]
(Optional)

Specifies the type of results returned by the trace.

  • SELECTION — The trace results are returned as a selection set on the appropriate network features. This is the default.
  • AGGREGATED_GEOMETRY — The trace results are aggregated by geometry type and stored in feature classes displayed in layers on the active map.
  • NETWORK_LAYERS —The trace results are added to feature layers as a selection set inside of a group layer.
String
selection_type

Specifies how the selection will be applied and what to do if a selection already exists.

  • NEW_SELECTION —The resulting selection replaces the current selection. This is the default.
  • ADD_TO_SELECTION —The resulting selection is added to the current selection if one exists. If no selection exists, this is the same as the new selection option.
  • REMOVE_FROM_SELECTION —The resulting selection is removed from the current selection. If no selection exists, this option has no effect.
  • SUBSET_SELECTION —The resulting selection is combined with the current selection. Only records that are common to both remain selected.
  • SWITCH_SELECTION —The resulting selection is switched. Results that were selected are removed from the current selection; while results that were not selected are added to the current selection. If no selection exists, this is the same as the new selection option.
String
clear_all_previous_trace_results
(Optional)

Specifies whether content will be truncated from or appended to the feature classes chosen to store aggregated geometry. This parameter is only applicable to the aggregated geometry result type.

  • CLEAR_ALL_PREVIOUS_TRACE_RESULTS — The feature classes storing aggregated trace geometry will be truncated. Only the output geometry from the current trace operation will be written. This is the default.
  • DO_NOT_CLEAR_ALL_PREVIOUS_TRACE_RESULTS —The output geometry from the current trace operation will be appended to the feature classes storing aggregated geometry.
Boolean
trace_name
(Optional)

The name of the trace operation. This value is stored in the TRACENAME field of the output feature class to assist with identification of the trace results. This parameter is only applicable to the aggregated geometry result type.

String
aggregated_points
(Optional)

An output multipoint feature class containing the aggregated result geometry. By default, the parameter is populated with a system-generated feature class named Trace_Results_Aggregated_Points that will be stored in the project's default geodatabase.

This feature class will be created automatically if it does not exist. An existing feature class can also be used to store aggregated geometry. If a feature class other than the default is used, it must be a multipoint feature class and contain a string field named TRACENAME. This parameter is only applicable to the aggregated geometry result type.

Feature Class
aggregated_lines
(Optional)

An output polyline feature class containing the aggregated result geometry. By default, the parameter is populated with a system-generated feature class named Trace_Results_Aggregated_Lines that will be stored in the project's default geodatabase.

This feature class will be created automatically if it does not exist. An existing feature class can also be used to store aggregated geometry. If a feature class other than the default is used, it must be a polyline feature class and contain a string field named TRACENAME. This parameter is only applicable to the aggregated geometry result type.

Feature Class
out_network_layer
(Optional)

The name of the output group layer that contains feature layers with selection sets of features returned by the trace. The layer provides access to work with the output of a trace in ModelBuilder and Python.

This parameter is only applicable to the network layers result type.

Group Layer
use_trace_config
(Optional)

Specifies whether an existing trace configuration will be used to populate the parameters of the Trace tool.

  • USE_TRACE_CONFIGURATION —The trace will use an existing trace configuration to define the properties of the trace. All parameters except trace_config_name, starting_points, and barriers are ignored.
  • DO_NOT_USE_TRACE_CONFIGURATION —The trace will not use a trace configuration to define the properties of the trace. This is the default.
Note:

This parameter requires Trace Network Version 2 or later.

Boolean
trace_config_name
(Optional)

Specifies the name of the trace configuration that will be used to define the properties of the trace. This parameter is only enabled when the use_trace_config parameter is set to USE_TRACE_CONFIGURATION.

Note:

This parameter requires Trace Network Version 2 or later.

String

Derived Output

NameExplanationData Type
updated_trace_network

The updated trace network.

Any Value

Code sample

Trace example (Python window)

Run a downstream trace on a trace network named HydroNetwork using the Trace function.

import arcpy
arcpy.Trace_tn(r"C:\MyProject\NHD.gdb\Hydro\HydroNetwork", 
               "DOWNSTREAM", r"C:\MyProject\NHD.gdb\TN_Temp_Starting_Points")

Environments

This tool does not use any geoprocessing environments.

Licensing information

  • Basic: No
  • Standard: Yes
  • Advanced: Yes

Related topics

  • An overview of the Trace Network toolbox
  • Find a geoprocessing tool

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In this topic
  1. Summary
  2. Usage
  3. Syntax
  4. Code sample
  5. Environments
  6. Licensing information