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Trace a utility network

On the ArcGIS platform, utility networks offer a framework for modeling utility systems, such as, electric, gas, water, storm water, wastewater, and telecommunications. Each utility network demonstrates how features are connected and how dynamic devices are configured. For more information about utility networks, see ArcGIS Pro's help topic What is a utility network?. This topic describes how to build ArcGIS Runtime apps that can trace the flow of resources, such as gas, water, and electricity, through its network. You can explore how a network is affected by real-world events such as storms, outages, or equipment failure, by asking certain questions, for example,

  • How is your network connected?
  • How does electricity/gas/water reach your house?
  • If a device is disabled, what section of the network will be out of power?

To help answer these questions, ArcGIS Runtime supports upstream, downstream, subnetwork, and connected utility traces. To trace a utility network you need to:

  1. Access the utility network
  2. Define the trace parameters
    1. Decide which trace to perform
    2. Define the starting and barrier locations
    3. Specify the trace configuration
  3. Execute the trace
  4. Examine the results

Access the utility network

Utility networks are implemented in service-based geodatabases as network controller datasets. These datasets contain a network's service feature tables along with the network's domains, sources, tiers, assets, terminals, rules and associations. This utility network is accessible via these service feature tables stored in a single feature service.

You can display and share a complete utility network with a user via a web map if the map includes one feature layer for every network source.

Diagram of objects loaded when loading a utility network with a map with layers for all network sources.

To display and share the utility network, create a utility network object from a feature service URL and a web map that contains all the layers that participate in the utility network.

var utilityNetwork = AGSUtilityNetwork(url: featureServiceURL, map: map)

Note:

The feature service provides access to the topological network in the utility network. So, you could provide a map that contains just a subset of the feature layers, for a specific workflow. Any tracing would be performed using the full topological network provided by the feature service. If you need to add additional utility network layers you can create them from the individual network sources, as required.

You can also access a utility network and run a trace completely without a map. Just provide the feature service URL when you create the utility network. If needed, you can create a completely new map by creating feature layers from the network sources.

var utilityNetwork = AGSUtilityNetwork(url: featureServiceURL)

Note:

ArcGIS Runtime supports Utility Network version 2 and later that is provided from ArcGIS Pro 2.2 onwards. For details see utility network upgrade history.

Load the utility network

The utility network follows the loadable pattern for asynchronous resources. Loading the utility network loads the entire utility network schema (information about the datasets that participate in the network). Once loaded, your app can navigate this network schema to discover the domain networks it contains and any further details about the network.

utilityNetwork.load { [weak self] error in
 if let error = error {
  print("Loading Utility Network Failed")
  return
 }

 //continue with the utility network
 print("The Utility Network schema version is \(self?.utilityNetwork.definition.schemaVersion)")

}

Define the trace parameters

Trace parameters define how the trace analysis proceeds across the utility network. These are the essential trace parameters:

  1. Trace type
  2. Start and barrier locations
  3. Trace configuration

Trace type

This version of the ArcGIS Runtime SDK supports four different types of utility network trace:

Upstream trace

In a source-based network (gas or electric), an upstream trace is against the flow and toward the source, such as a circuit breaker or generator (subnetwork controller). In a sink-based network (sewer or storm water), an upstream trace is against the flow and away from the sink such as a sewage treatment (subnetwork controller).

For more details see upstream trace.

Downstream trace

In a source-based network (gas or electric), a downstream trace is with the flow and away from the source, such as a circuit breaker or generator (subnetwork controller). In a sink-based network (sewer or storm water), a downstream trace is with the flow and toward the sink such as a sewage treatment (subnetwork controller).

For more details see downstream trace.

Subnetwork trace

A subnetwork trace discovers all features participating in a subnetwork. This trace type is useful for validating whether subnetworks, such as circuits or zones, are defined or edited appropriately.

The trace begins at one or more starting points and spans outward along connected features to find subnetwork controllers that are traversable. A subnetwork trace stops when it encounters a barrier, a feature that is not traversable, or when there are no more connected features.

For more details see subnetwork trace.

Connected trace

A connected trace begins at one or more starting points and spans outward radially along connected features. A trace stops when a barrier is encountered or there are no more connected features. This type of trace is useful for validating newly edited features are connected as expected.

For more details see find connected features.

Use the utility trace type to create the parameters

Create a set of AGSUtilityTraceParameters by providing a AGSUtilityTraceType of upstream, downstream, subnetwork, or connected, along with a collection of starting locations (if known at this stage).

var utilityTraceParameters = AGSUtilityTraceParameters(traceType: .upstream, startingLocations: [])

Start and barrier locations

Each trace requires a start location from which to initiate the trace. You can create a start location from a specific feature, as follows:

  1. Get the network source for the feature.
    1. Get the ArcGIS feature table for the feature.
    2. Get the network source represented by the ArcGIS feature table using the table name.

    let featureTable = startingFeature.featureTable as? AGSArcGISFeatureTable
    
    let networkSource = utilityNetwork.definition.networkSource(withName: featureTable.tableName)

  2. Create a utility element for the feature. You must adopt different code patterns, depending on whether the utility network source is a junction or an edge.
    1. If the utility network source is a junction, find the available terminals for that feature using the utility network definition. If more than one terminal is found, select a terminal to use. Create the utility element from the feature and set the terminal.

      switch networkSource.sourceType {
       case .junction:
        
       // Create the utility element from the feature 
       guard let utilityElement = utilityNetwork.createElement(with: feature) else {return}
               
       guard let terminals = utilityElement.assetType.terminalConfiguration?.terminals else {return}
       let terminal = terminals[0]
                  
       utilityElement.terminal = terminal               
      
      }

    2. If the utility network source is an edge feature, create the utility element from the feature. Set the fractionAlongEdge value to represent the location of the starting point or barrier along that edge.

      switch networkSource.sourceType {
       case .edge:
                      
        // Create the element from the feature  
        guard let utilityElement = utilityNetwork.createElement(with: feature, terminal: nil) else {return}
      
        // Determine how far the starting point or barrier is located along an edge
        let geometry = feature.geometry
        let line = AGSGeometryEngine.geometryByRemovingZ(from: geometry) as? AGSPolyline 
        utilityElement.fractionAlongEdge = AGSGeometryEngine.fraction(alongLine: line, to: mapPoint, tolerance: -1)
                          
      }

  3. Add the utility element to the utility trace parameters’ startingLocations collection.

    self.utilityTraceParameters.startingLocations.append(utilityElement)

  4. If you need to add a barrier, complete the steps 1 and 2 above and add the utility element to the utility trace parameters’ barriers collection.

Trace configuration

You can enhance a trace as using the trace configuration that is set on the AGSUtilityTraceParameters. With the trace configuration you could:

  • stop the trace at protective devices if they are open. For example, the flow of electricity in a network will be stopped if a fuse is open
  • control the types of features traced (pipe diameter greater than 6 inches)

Each trace configuration manages basic properties such as:

  • Include barriers in trace results
  • Include containers in trace results
  • Include content in trace results
  • Include structures in trace results
  • Ignore barriers if they are the starting points
  • Domain network
  • Source tier
For more advanced properties, such as traversability, propagators and target tiers see the advanced trace configuration section.

When a utility network administrator creates a new tier in ArcGIS Pro, a subnetwork trace configuration is created and populated as described in Configure a trace.

You can choose if your app uses the trace configuration as defined by an administrator, you modify this configuration, or whether you create your own trace configuration.

Use a trace configuration defined in a utility network tier

To obtain the trace configuration from a utility network tier, you need to know the name of the domain network and the tier, as follows:

  1. Obtain the utility network definition from the utility network.
  2. Get the domain network from the utility network definition.
  3. Obtain the tier from the domain network.
  4. Pass the tier's trace configuration to the utility trace parameters.
  5. Modify any of these properties as required.

    let utilityNetwork = AGSUtilityNetwork(url: theFeatureServiceURL)
            
    utilityNetwork.load {[weak self] (error) in
    
     //get the network domain called "ElectricDistribution"
     guard let utilityNetworkDomain = utilityNetwork.definition.domainNetwork(withDomainNetworkName: "ElectricDistribution") else {
      print("Utility Network Domain not found")  
      return
     }
        
     //get the tier called "Medium Voltage Radial"          
     guard let utilityTier = utilityNetworkDomain.tier(withName: "Medium Voltage Radial") else {
      print("Utility Tier not found")          
      return
     }
     
     //get the tier's traceconfiguration
     let traceConfiguration = utilityTier.traceConfiguration
    
     self?.utilityTraceParameters.traceConfiguration = traceConfiguration
    }

Create your own trace configuration

You can create your own trace configuration.

  1. Create a utility trace configuration.
  2. If you are running an upstream, downstream, or subnetwork trace then you must set the domain network as follows:
    1. Obtain the domain network from the utility network definition.
    2. Pass the domain network to the utility trace configuration.
  3. Modify any of the other properties, as required
  4. Pass the utility trace configuration to the utility trace parameters.

    let utilityNetwork = AGSUtilityNetwork(url: theURL)
    
    utilityNetwork.load { (error) in
        
     if let error = error { print(error.localizedDescription)
      return
     }      
     
     //create the utility trace configuration
     let traceConfiguration = AGSUtilityTraceConfiguration()
    
     //set the network domain called "ElectricDistribution" on the utility trace configuration
     guard let utilityNetworkDomain = utilityNetwork.definition.domainNetwork(withDomainNetworkName: "ElectricDistribution") else {
      return
     }            
     traceConfiguration.domainNetwork = utilityNetwork.definition.domainNetwork(withDomainNetworkName: "ElectricDistribution")
            
     //modify any other parameters, as required
       
     self?.utilityTraceParameters.traceConfiguration = traceConfiguration         
    }

Execute the trace

Run the trace by calling the trace method on the utility network object. Use the utility trace parameters defined in the previous section. In the current release of ArcGIS Runtime SDK, all utility trace results are returned as utility element trace results.

// Perform the trace
utilityNetwork.trace(with: self.utilityTraceParameters) { [weak self] (utilityTraceResult, error) in
 if let error = error {
  print(error)
  return
 }
            
 //process the trace result
 ...

}

If the trace fails you can examine why. For example, failure could be due to dirty areas in the network topology.

Examine the results

To display the results of this trace on a map, or to analyze them further, you need to obtain the corresponding features for these elements. Do this as follows:

  1. Filter the utility element trace results to find those that are part of the map, and group them by network source name.
  2. For every group (network source with utility elements), make sure there is a layer in the map for the features. Next find the features corresponding to the utility elements.

    guard let elementTraceResult = traceResult.first as? AGSUtilityElementTraceResult,
      !elementTraceResult.elements.isEmpty 
      else {
      print("Trace returns no results")
      return
    }
    
    let groupedElements = Dictionary(grouping: elementTraceResult.elements, by: { $0.networkSource.name })
    
    for (networkSourceName, elements) in groupedElements {
     
     // ensure that the features' layer exists in the map 
     guard let layer = self.map.operationalLayers.first(
      where: { ($0 as? AGSFeatureLayer)?.featureTable?.tableName == networkSourceName }) as? AGSFeatureLayer 
      else { continue }
    
     // get the features that correspond to the elements
     self.utilityNetwork.features(for: elements, completion: { [layer, networkSourceName] (features, error) in
    
     guard let features = features else { return }
    
     })
    }

  3. Select the features that correspond to the trace result or process as required.

    // Select features to highlight result
    layer.select(features)

Advanced trace configuration

The trace configuration has a few advanced properties that will be discussed here:

Traversability

As you trace a topological network you can examine a number of constraints or conditions that could stop the trace. For example, you can stop tracing the network if:

  • a water valve is closed
  • an electric switch is open
  • a distance of 1000 m is reached
  • if the gas pipe is made of plastic
The ability for a trace to traverse the topological network is defined by the traversability property on the AGSUtilityTraceConfiguration class. You can set conditions or constraints to this trace using barriers and function barrier properties.

Barriers

Set up a trace barrier by comparing the value of an asset's attribute or by examining the existence of a UtilityCategory. You can compare them individually or combine them with boolean And / Or operations into complex filters.

  • Use the AGSUtilityNetworkAttributeComparison class to compare an element's network attribute. For example, compare an attribute value to:
    • a specific value (for example, "DeviceStatus not equal to 4"), and/or
    • another network attribute on the same element (for example, "SeasonalDeviceStatus" <> "NormalDeviceStatus")

    guard let lifecycleNetworkAttribute = utilityNetwork.definition.networkAttribute(withName: "Lifecycle") else {return}
                
    // Create a network attribute comparison that stops traversal if Lifecycle <> 4)
    let inDesignNetworkAttributeComparison = AGSUtilityNetworkAttributeComparison(networkAttribute: lifecycleNetworkAttribute, comparisonOperator: .notEqual, value: 4)
                
    // Create a network attribute comparison to stop traversal if Lifecycle <> 8
    let inServiceNetworkAttributeComparison = AGSUtilityNetworkAttributeComparison(networkAttribute: lifecycleNetworkAttribute, comparisonOperator: .notEqual, value: 8)
                
    // Combine these two comparisons together with "And"
    let lifecycleFilter = AGSUtilityTraceAndCondition(leftExpression: inDesignNetworkAttributeComparison, rightExpression: inServiceNetworkAttributeComparison)
                
    // Final condition stops traversal if Lifecycle <> 4 and Lifecycle <> 8
    traceConfiguration.traversability?.barriers = lifecycleFilter

  • Check a utility element's asset type to see whether that asset type (and thus the element) is included in a specific category using the AGSUtilityCategoryComparison class.

Function barriers

You can create a function barrier to terminate network traversal whenever a function expression evaluates to true. The function barrier compares the current results of a function and a given value. For example, you can use the function barrier to stop traversal after the trace traverses 1000 m along the network.

//create a network attribute object for the Shape length network attribute from the utility network definition
guard let shapeLengthNetworkAttribute = utilityNetwork.definition.networkAttribute(withName: "Shape length") else {return}
            
//create a function that adds up shape length
let lengthFunction = AGSUtilityTraceFunction(functionType: .add, networkAttribute: shapeLengthNetworkAttribute)
            
//create a function barrier that stops traversal after 1000 meters
let distanceBarrier = AGSUtilityTraceFunctionBarrier(traceFunction: lengthFunction, comparisonOperator: .greaterThan, value: 1000.0)
            
//set this function barrier
traceConfiguration.traversability?.functionBarriers.append(distanceBarrier)

For more information see traversability.

Note:

The AGSUtilityTraversabilityScope property determines whether these conditions are evaluated on edges, junctions, or both.

Propagators

A propagator defines the propagation of a network attribute along a traversal and provides a filter to stop traversal. Propagators are only applicable to subnetwork-based traces (subnetwork, upstream, or downstream). One example is electric phase propagation, where open devices along the network will restrict some phases from continuing along the trace.

//get a network attribute object for the "Phases Normal" attribute from the utility network definition
guard let networkAttribute = utilityNetwork.definition.networkAttribute(withName: "Phases Normal") else {return}

//create a propagator to propagate the attribute using a Bitwise And function
let propagator = AGSUtilityPropagator(networkAttribute: networkAttribute, propagatorFunctionType: .bitwiseAnd, comparisonOperator: .includesAny, value: 7)

//assign the propagator to the trace configuration
traceConfiguration.propagators.append(propagator)

For more information see propagators.

Target tiers

All upstream and downstream traces can operate across the current tier (source tier). If you want your upstream or downstream trace to continue into another tier, you set the targetTier property on the AGSUtilityTraceConfiguration.

Tracing considerations

Dirty areas

All tracing operations rely on a topological network that is built from the utility network. If the network has been edited but the topological network is out of date then it can contain dirty areas. For more information see validate the network topology. If the topological network has dirty areas you can adopt a different approach depending on your app's purpose:

  • If the app must trace with the latest data (for example, an outage management app), an error should be returned to the user if it encounters a dirty area.
  • If the app can trace with a network that is out of sync with the feature (for example, a pole inspection app), then you should consider whether to set validateConsistency to false on the AGSUtilityTraceConfiguration. You can optionally display a warning to the user if a dirty area is encountered.

Get associated utility elements

Associations model three types of relationships between features:

  • Connectivity associations model the connectivity between two junctions that don't have geometric coincidence (are not in the same x, y and z location).
  • Structural attachment associations model equipment attached to structures.
  • Containment associations model features encased within other features.
Each association is defined between two AGSUtilityElement objects. You can identify which AGSUtilityElements are associated with a given AGSUtilityElement using the associations method on the AGSUtilityNetwork.

//get the elements associated with a single utility element (using containment)
utilityNetwork.associations(with: utilityElement, type: .containment) { (associations, error) in
 if let error = error {return}
 guard let associations = associations else {return}
                
  for association in associations {
   let fromElement = association.fromElement
   let toElement = association.toElement
  }
}

For more information see ArcGIS Pro's help topicAssociations.