Exercise 5: Building a geometric network
Feature classes stored in the same feature dataset can participate in a geometric network. Geometric networks model directed flow network systems such as water networks. You will build a geometric network from the feature classes in the Water feature dataset in the Montgomery geodatabase. You will then create connectivity rules to define which features can connect to each other in the network.
Creating the water network
- Start ArcCatalog by clicking Start > All Programs > ArcGIS > ArcCatalog 10.
- Navigate to the Montgomery geodatabase in your Folder Connections.
- Expand the Montgomery geodatabase.
Right-click the Water feature dataset in the Montgomery geodatabase, point to New, then click Geometric Network.
The New Geometric Network wizard opens.
- Click Next.
- Type WaterNet for the name of the geometric network.
- Click Yes to snap features.
Type 0.5 in the text box next to Feet.
The dialog box should look similar to this.
- Click Next.
Click Select All.
All the feature classes in the list will participate in the network.
- Click Next.
Click No, so that all features will participate in the geometric network.
- Click Next.
- In the row for the Distribmains, click Simple edge under the Role column.
Choose Complex edge from the list.
This changes the role for the Distribmains feature class from a simple edge to a complex edge.
- In the row for the Tanks feature class, click the drop-down menu under Sources & Sinks, then click Yes.
In the row for Transmains, click Simple edge under the Role column, then choose Complex edge from the list.
This changes the role for the Transmains feature class from a simple edge to a complex edge.
- Click Next.
This geometric network does not require weights, which is the default, so click Next.
Clicking Next opens a summary page.
Click Finish after you review the summary page.
A progress indicator appears displaying the progress for each stage of the network-building process.
You will receive an error message indicating the network built, but with errors.
- Click OK to close the message box.
- You can see what errors occurred while building the geometric network by previewing the WaterNet_BUILDERR table.
Click the WaterNet_BUILDERR table in the Catalog tree and click the Preview tab to view the entries in this table.
Two records are displayed.Tip:
If you received more than two errors, delete the geometric network and repeat the steps to create it again. Be sure you correctly complete all the steps in this exercise to create the geometric network. If you still have more than two errors, it could be that you did not complete the preceding 5 exercises. This tutorial is cumulative; you must complete the preceding exercises before doing this one.
You must now select which feature classes in the feature dataset will participate in the geometric network
The option to exclude features with certain attributes makes it easier to manage the state of parts of the network if you need to drop the network and rebuild it after you have been working with it for awhile. On the next panel, you will opt not to exclude features.
On the next dialog box, you must specify which line classes will become complex edge feature classes in the geometric network. Complex edge features are not split into two features by the connection of another feature along their length; thus, they are useful for modeling water mains, which may have multiple laterals connected to them. By default, all line feature classes are simple edge feature classes.
On the same dialog box, you must specify which, if any, of the junction feature classes can act as sources and sinks in the network. Sources and sinks are used to determine the flow direction in the network.
Now you can assign network weights. A network weight describes the cost of traversing an element in the logical network, such as the drop in pressure as water flows through a pipe.
Next, you will establish connectivity rules for your water network.
Creating connectivity rules
Network connectivity rules constrain the type of network features that may be connected to each other and the number of features of any particular type that can be connected to features of another type. By establishing these rules, you can maintain the integrity of the network connectivity in the database.
Right-click the WaterNet geometric network in the Water feature dataset and click Properties.
The Geometric Network Properties dialog box opens, which provides information about feature classes participating in the network and a list of the network weights. You can also add, delete, and modify connectivity rules using this dialog box.
Click the Connectivity tab.
This tab lets you add and modify connectivity rules for the geometric network.
- Click the drop-down arrow and click laterals.
- Click Hydrant laterals in the Subtypes in the feature class list.
- Check Hydrants in the Subtypes in the network list.
Click the plus sign next to Hydrants in the Subtypes in the network list.
The Hydrants subtype is expanded.
Right-click Hydrants under the Hydrants subtype and click Set as Default.
A blue D appears next to the hydrant subtype, indicating that it is the default junction for this edge subtype.
- Click the plus sign next to Distribmains in the Subtypes in the network list to expand it.
- Check Distribmains, which appears under the Distribmains subtype.
- Click the plus sign to expand Fittings in the Junctions subtype list.
Check Tap, Tee, and Saddle, in that order, under the Fittings junction subtype.
Tap has a blue D next to it, indicating it is the default junction.
- Also in the Junctions subtype list, check WaterNet_Junctions, which is the generic, or default, network junction type.
- Click OK.
You will first create a new edge–junction rule, which states that hydrants can connect to hydrant laterals; it also indicates that when a hydrant lateral is created, a hydrant junction feature should be placed at its free end.
You will now click the types of junctions that hydrant laterals can connect to in the network. For simplicity, hydrant laterals can only connect to hydrants.
You should also specify that when you create a hydrant lateral, if an end of the lateral is not connected to another edge or junction, then a hydrant is placed at that end.
You will now create a new edge–edge rule, which states that hydrant laterals can connect to distribution mains through taps, tees, and saddles. The default junction for connections between hydrant laterals and distribution mains will be taps.
Because you have checked an edge in the network subtypes list, the list of junction subtypes in the network becomes active. In this list, you can specify which junction types hydrant laterals and distribution mains can connect through.
You have now added behavior to your geodatabase by defining connectivity rules. You would normally define many more connectivity rules for a network. However, for this tutorial, you only need to define the connectivity rules specified here.
In Exercise 6: Creating annotation, you will create feature-linked annotation for your new hydrant lateral feature class.