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Problem: Edges have indeterminate flow after setting flow direction

Description

After setting the flow direction with the Set Flow Direction command on the Utility Network Analyst toolbar, the edges are expected to show a flow direction, but they show an indeterminate flow instead.

Cause

Indeterminate flow in a network occurs when the flow direction cannot be uniquely determined by the Set Flow Direction command. Indeterminate flow commonly occurs for edges that form part of a loop, or closed circuit.

Indeterminate flow can also occur for an edge whose flow is determined by multiple sources, multiple sinks, or a mixture of sources and sinks in the network. In these cases, the edge has indeterminate flow because one source or sink is driving the flow in one direction through the edge, but another source or sink is driving it in the opposite direction. One example of this is an edge that has a source at both of its ends will have indeterminate flow. Another example can be seen by following the link on the first item of the Related Information section below.

Solution or Workaround

 

  1. Display the flow direction arrows so that the indeterminate flow and uninitialized flow symbols are different from each other.
    See: How To: Identify edges with uninitialized and indeterminate flow in a geometric network
  2. Run the Find Loops trace task from an edge with indeterminate flow to determine whether the edges with indeterminate flow form a cycle in the network.
  3. If an edge with indeterminate flow does not form a cycle in the network, then the flow direction of the edge is indeterminate due to conflicting sources and/or sinks in the network.
    See: FAQ: How can edges have indeterminate flow after setting flow direction with multiple sources and sinks?
    Make sure that there is only one source or sink present for each connected component of edges.
  4. If an edge forms a cycle in the network, then the flow direction of the edge is indeterminate due to the cycle in the network. If the cycle is not desired, edit the connectivity of the network features to remove the cycle. If the cycle is desired, then flow direction cannot be set with the Set Flow Direction command.
  5. For alternative methods of setting the flow direction in a geometric network, see the flow direction developer samples in the ArcObjects Developer Help under Samples > Network > Utility Network Analysis.

Related Information