Trace is a network management task that ensures optimal paths exist for resources to travel. The trace network's trace functionality provides a framework you can use to track the flow of resources, analyze the health of a network, and identify areas for closer examination.
Trace results are based on connectivity and traversability within the network topology. A network element is returned in a trace result only when it is connected or associated with other elements in the trace result. The trace result is the set of network features that is found by the trace operation.
A trace begins at one or more starting points and spans outward based on the flow direction set in the network. It travels through the network along paths of connected features until it reaches an end location. The end location can be a barrier or the end of a path. Upon completion, the results of a trace are returned as either a selection set or multipart feature class. The results can be used for further analysis. For example, a resulting selection set can be used as input to a reporting function or propagated to other map or diagram views.
Connectivity and traversability
There are two terms used to describe how network features are related to one another. Connectivity describes the state in which two features have geometric coincidence-based connectivity . Traversability describes the situation in which two features are connected and have appropriate attributes. The attributes and attribute values considered during a trace are controlled by configurations set up through geoprocessing tools.
Tracing operations travel a network by one of two methods: connectivity or traversability. The method a trace uses is controlled by the type of trace used. The Advanced Options parameters in the Trace tool control the details of traversability traces.
The Trace tool is used to run traces on a trace network and includes a set of standard traces that can be configured to create complex traces.
To learn more about the tool, see Trace.
The parameters and advanced options provided with the Trace tool allow you to refine which features are traced and which are returned in the results.
The Trace tool relies on the network topology; it reads cached information about features from the network topology rather than the map. By reading cached information, performance is improved during complex traces on large networks. Because of this, the results of a trace are not guaranteed to be accurate if dirty areas exist in the traceable area. The network topology for the traceable area must be validated to ensure it reflects the most recent edits or updates made to the trace network.
To learn more about trace configurations, see Configure a trace.
Trace network trace types
There are four network traces available with the trace network:
- Connected trace—A connected trace begins at one or more starting points and spans outward along connected features. A trace travels along a path and stops when either a barrier is encountered or there are no more connected features (the end of a path). This type of trace is useful for confirming that newly edited features are connected as expected.
- Upstream trace—An upstream trace discovers features upstream from a location in the network. This type of trace respects the flow direction set on network edges.
- Downstream trace—A downstream trace discovers features downstream from a location in the network. This type of trace respects the flow direction set on network edges.
- Shortest path trace—This type of trace finds the shortest path between two starting points in the network, regardless of flow direction. The cost of traversing the path is determined either through a numeric attribute, such as shape length, or based on the network attribute set for the Shortest Path Network Attribute Name parameter value.
You can change the criteria of a trace using the Trace tool. By default, results from a trace operation are returned as a selection set on the appropriate network features. Trace results include any features meeting the tracing criteria between a starting point and a barrier or the end of a path (no more connected features). The optional Result Types parameter provides four options in addition to the default of Selection to control the type of results returned by the trace.
The Aggregated Geometry result types option enables aggregated geometry of the point and line features to be returned as multipart feature classes by the trace and honors midspan starting points and barriers to return partial feature geometry.
The Network Layers result types option allows you to return trace results as selection sets on feature layers in a group layer. When this option is selected in ArcGIS Pro, a new group layer is added to the map. Feature layers are only created for classes that contain features returned by the trace. Each feature layer contains a selection set of features returned by the trace that can be used to work with the results of a trace in ModelBuilder and Python.
The Connectivity result types option returns trace results as a connectivity graph of network features connected through geometric coincidence. When this option is selected, connectivity is output to a .json file in the specified location that can be parsed and imported into other systems to build your own graph representation of the data. Connectivity information is only returned for network features returned by the trace.
The Elements result types option returns trace results as feature-based information. When this option is selected, feature-based information is output to a .json file in the specified location that can be used as an input to perform additional analysis.
To include the System Junctions layer in trace results, you must first make the layer selectable. Click List by Selection to display your layers in the Contents pane and click the System Junctions check box to make it selectable.
The Apply To Diagrams tool is used to propagate the selection set in a map view to a diagram view.
To remove trace results from a map, click the Clear Selection button.