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.
Starting points can be created through the Trace Locations pane or by specifying an existing feature class in the Starting Points parameter of the Trace tool. Only network features can be selected as starting points when the Trace Locations pane is used, . When a network feature is either selected or added to the pane from a selection set, a coincident point is created to denote the start location for the trace. When working with lines, a starting point can be placed anywhere along the line feature. With this option, starting points are created and managed on the Starting Points tab. This tab can be accessed from the Tools group of the Trace Network ribbon. In the Trace Locations pane, you can set multiple starting points; specify point, line, and polygon features; differentiate between coincident features; and add features selected on the map to act as starting points.
When a starting point is established using the Trace Locations 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
.
When an existing feature class is used to supply starting points for the Trace tool, if the source feature class shares the necessary schema from the TN_Temp_Starting_Points feature class, SOURCEID and FEATUREGLOBALID are read and applied to the corresponding network feature as a starting point. In scenarios where these fields are not populated, features without a corresponding value will not be used to place a starting point. This option is helpful when you want to maintain granularity over which features act as starting points where coincident geometries exist. If the SOURCEID and FEATUREGLOBALID fields are not present in the schema of the feature class, the geometry of the input feature class is used to intersect the network feature geometry and place starting points.
Keep the following information in mind when using existing feature classes as starting points:
- The TN_Temp_Starting_Points feature class is not used with this method.
- Selection sets on the input feature class are not honored.
- For polygons, starting points are placed along the boundary where network features intersect the polygon geometry.
Note:
By default, trace results are returned as a selection and include the entire line feature. When a starting point is placed midspan on an edge feature, the Result Types option Aggregate Geometry can be specified to return partial feature results in an output multipart geometry feature class.