Network analysis workflow
Whether you are performing a route, service area, or other network analysis in ArcGIS Network Analyst, the workflow is similar. This topic presents the general procedure for solving network problems.
This is a general topic about the workflow for performing any network analysis. Structured exercises for performing specific network analyses are available in the ArcGIS Network Analyst Tutorial. The first two tutorial exercises describe creating network datasets; the other exercises step through the process of performing the various analyses ArcGIS Network Analyst offers.
The basic steps to perform any type of network analysis in ArcGIS Network Analyst include the following:
- Configuring the Network Analyst environment
- Adding a network dataset to ArcMap
- Creating the network analysis layer
- Adding network analysis objects
- Setting network analysis layer properties
- Performing the analysis and displaying the results
Step 1: Configuring the Network Analyst environment
Network Analyst is an extension to ArcGIS. Thus, you must enable the Network Analyst extension prior to performing any network analysis. You also need to display the Network Analyst toolbar and, from there, show the Network Analyst window. The steps to accomplish this are covered in Configuring the Network Analyst extension.
Step 2: Adding a network dataset to ArcMap
Before you can perform a network analysis, you need to have a network on which to perform the analysis. Therefore, your next step is to add a network dataset layer to ArcMap. If the network has not been built, you'll need to build it. If the source features have been edited or the network attributes that reference the source features have changed, you need to rebuild the network dataset.
Step 3: Creating the network analysis layer
A network analysis layer stores the inputs, properties, and results of a network analysis. It contains an in-memory workspace with network analysis classes for each type of input, as well as for the results. The features and records inside the network analysis classes are referred to as network analysis objects. Some properties of the network analysis layer allow you to further define the problem you want to solve.
Network analyses are always performed on network datasets. Consequently, a network analysis layer must be bound to a network dataset. If you make a network analysis layer using a geoprocessing tool, you will set the network dataset as a tool parameter. In ArcMap, a network dataset must be added first so that when an analysis layer is created, Network Analyst can bind the analysis layer to the network dataset.
When a network dataset is added to ArcMap, it is referred to as a network dataset layer, or simply a network layer.
Network layers represent network datasets, whereas network analysis layers represent the inputs, properties, and results of network analyses.
There are six kinds of network analysis layers:
- Route analysis layer
- Closest facility analysis layer
- Service area analysis layer
- OD cost matrix analysis layer
- Vehicle routing problem analysis layer
- Location-allocation analysis layer
Step 4: Adding network analysis objects
Network analysis objects are features and records used as input and output during network analysis. Examples include stops, barriers, routes, and facilities.
You can add network analysis objects to input classes, but you won't be able to add them to output-only classes. Output-only network analysis objects can only be created by the solver. For instance, the Route class in a route analysis layer is output only, so route objects can only be created by the solver.
There are different ways to add objects to classes. The two most commonly chosen options are: one, loading several features into a network analysis class at once, two, interactively adding one object at a time.
As you add objects, you set their individual properties. These properties further define their function as input.
Step 5: Setting network analysis layer properties
The network analysis layer also has properties that are more general to the analysis than those of its network analysis objects. The general analysis properties are the network impedance attribute to use, the restriction attributes to obey, and so on. Additionally, there are properties that are unique to the kind of analysis being performed. The Layer Properties dialog box of an analysis layer provides access to these properties.
Step 6: Performing the analysis and displaying the results
Once you have created your analysis layer, added input network analysis objects, and set the parameters for the analysis objects and analysis layer, it is time to solve the network problem.
Click the Solve button on the Network Analyst toolbar.
Network Analyst generates the solution, which becomes part of the network analysis layer. The output network analysis objects are created and the input/output objects are updated with results.
You can look at the map and double-click the network analysis objects in the Network Analyst window to inspect the results.