Starting points

Starting points are used to define the location in the network where a trace will begin. All trace operations in the trace network require that one or more starting points be defined. You can create starting points in the Trace pane or by specifying a user-defined feature class for the Starting Points parameter of the Trace tool.

When you use the Trace pane, starting points are created and managed on the Starting Points tab. You can access this tab from the Tools group of the Trace Network tab. In the pane, you can set multiple starting points, specify point and line features, differentiate between coincident features, and add selected features on the map to act as a starting point.

You can only select network features as starting points when using the Trace pane. When a network feature is selected or added to the pane from a selection set, the following are true:

• A coincident point is created to denote a starting point for the trace.
• When working with lines, a starting point can be placed anywhere along the edge.

When a starting point is established using the Starting Points tab in the Trace pane, a feature class named TN_Temp_Starting_Points is created in the project's default geodatabase. Successive starting points are appended to this class. To remove all starting points from a map, click the Clear All button on the Starting Points tab.

When an existing feature class or table is used to supply starting points for the Trace tool, take the following into consideration:

• The TN_Temp_Starting_Points feature class is not used with this method.
• Selection sets on the input feature class are not honored.
• For polygon features, starting points are placed along the boundary where network features intersect the polygon geometry.
• When working with an enterprise geodatabase, the following are requirements:
  • The schema of the user-defined feature class must contain a FEATUREGLOBALID field of type guid.
    • The FEATUREGLOBALID field must contain a Global ID from a corresponding network feature to be used as a starting point.
    • Features without a corresponding value are not used to place a starting point. This option can be used to provide granularity over which features act as starting points in a feature class.
  • The schema of the user-defined feature class must contain a PERCENTALONG field of type double to place starting points along an edge feature.
    • The PERCENTALONG field must contain a value between 0.0 and 1.0 to indicate the location of the starting point along the line.
    • If the PERCENTALONG field is not present, or does not contain an appropriate value, the trace assumes the starting point is placed on a junction feature and ignores placement along an edge.
• When working with a single-user geodatabase, the following are requirements:
  • The FEATUREGLOBALID field is not required. When absent, the geometry of the input feature class is used to intersect the network feature's geometry and place starting points.
    • When the FEATUREGLOBALID field is present, it must contain a Global ID from a corresponding network feature to be used as a starting point.
  • The PERCENTALONG field is not required. When absent, the geometry of the input feature class is used to intersect the network feature's geometry and place starting points.
    • When the PERCENTALONG field is present, it must contain a value between 0.0 and 1.0 to indicate the location of the starting point along a line. If the field is present and does not contain an appropriate value, the trace assumes the starting point is placed on a junction feature and ignores placement along an edge.

Note:

By default, trace results are returned as a selection and include the entire edge feature. When a starting point is placed midspan on an edge, the PERCENTALONG field is used to denote its location along the edge. The Result Types Aggregate Geometry option can be specified to return partial feature results in an output multipart geometry feature class.