The direction of flow in a trace network is determined by the flow direction set on network edge features. When the network topology is enabled for a trace network, a new system-maintained network attribute is created and assigned to all line feature classes that participate in the trace network. By default, flow is established with the digitized direction of a network edge. The Set Flow Direction tool can be used to update the flow direction of network edges at the feature class level or for a selected set of features.
The direction of flow can be set in three ways:
- With digitized direction—Flow direction is established along the digitized direction of edges. This is the default.
- Against digitized direction—Flow direction is established against the digitized direction of edges.
- Indeterminate direction—Flow direction is undetermined.
Requirements
Before you set the flow direction for line features in a trace network, the following requirements must be met:
The network topology must be enabled.
- Flow direction can only be set for line features that participate in the trace network.
- If a selection exists on network edge features, flow direction will be set on selected features only.
Caution:
When network features are validated or the network topology is disabled, the flow direction for network edges is reset. You can create an attribute to track the flow direction set for your features so this can be reconfigured when necessary.
Set the flow direction for a trace network
To set flow direction on line features in a trace network, complete the following steps:
- On the Analysis tab, in the Geoprocessing group, click Tools
to open the Geoprocessing pane. - In the Geoprocessing pane, search for and select the Set Flow Direction tool from the Trace Network toolbox.
- For the Input Trace Network parameter, specify the trace network that contains the line features for which you want to set flow direction.
- For the Feature Layers parameter, specify the network edge feature classes on which you want to set flow direction.
When a selection set exists on network edges on the map, the flow direction is set for those features only.
- For the Flow Direction parameter, choose the flow direction for the edge features.
- Click Run.
The flow direction is established for the selected features or the entire feature class.