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#Trace quantum gis code#

If local values are used, the local values along each path change, and the trace continues. In the global case, after you have traversed two edges with a value of 2, you have already reached a shape length sum of 4, so the trace stops. For example, a function barrier calculates the sum of shape length in which the trace terminates if the value is greater than or equal to 4.

Use Local Values-Calculate values in each direction as opposed to an overall global value.

Value-Provide a specific value for the input attribute type that, if discovered, will cause the termination.

Attribute-Filter by any network attribute defined in the system.

Function-Choose from a number of calculation functions.

When the total length traveled reaches the value specified, the trace stops.įunction barrier components are as follows: For example, the length of each line traveled is added to the total distance traveled so far. Function barriers can be used, for example, to restrict how far the trace travels from the starting point or to set a maximum value to stop a trace. Sets a traversability barrier on features based on a function.

Or-Use if either condition barrier is met.

Network Attribute-Filter by a network attribute.

Specific Value-Filter by a specific value.Is less than or equal to-The attribute is less than or equal to the value.Is less than-The attribute is less than the value.Is greater than or equal to-The attribute is greater than or equal to the value.Is greater than-The attribute is greater than the value.Does not equal-The attribute is not equal to the value.Is equal to-The attribute is equal to the value.You can combine them using an And or an Or condition. Combine using-Set this value if you have multiple attributes to add.Value-Provide a specific value for the input attribute type that would cause termination based on the operator value.Type-Choose a specific value or network attribute from the value specified in the Name component.Operator-Choose from a number of operators.Name-Filter by any network attribute defined in the system.

If you're using more than one attribute, you can use the Combine Using parameter to define an And or an Or condition.Ĭondition barrier components are as follows: When a feature meets this condition, the trace stops.

#Trace quantum gis code#

For example, stop a trace when a feature has the Code attribute equal to the specific value of ArtificialPath. A condition barrier uses a network attribute, an operator and a type, and an attribute value. Sets a traversability barrier condition on features based on a comparison to a network attribute.

The resulting selection set or output feature class generated by the trace can then be propagated to another map, propagated to a diagram view of the network, or used as input to another tool or trace. When a barrier is placed along an edge, trace results can be stopped at the nearest junction with midspan connectivity. When a starting point or barrier is placed on a junction with midspan connectivity, trace results will return partial elements of the edge feature. To return partial feature results, set the Result Types parameter to Aggregate Geometry. Traversability refers to paths established by connected features that also meet configurationīy default, trace results are returned as a selection and include the entire line feature. The trace capabilities of the trace network allow you to analyze paths in your network. Returns selected features in a trace network based on connectivity or traversability from the specified starting points.