Route analysis
Solving a route analysis can mean finding the quickest, shortest, or even the most scenic route, depending on the impedance you choose to solve for. If the impedance is time, then the best route is the quickest route. If the impedance is a time attribute with live or historical traffic, then the best route is the quickest route for a given time of day and date. Hence, the best route can be defined as the route that has the lowest impedance, or least cost, where the impedance is chosen by you. Any cost attribute can be used as the impedance when determining the best route.
This shows the route of the quickest path for someone to drive from point A to point B.
You can accumulate any number of impedance attributes in a route analysis, but accumulated attributes don't play a role in computing the path along the network. For example, if you choose a time cost attribute as the impedance attribute and want to accumulate a distance cost attribute, only the time cost attribute is used to optimize the solution. The total distance is accumulated and reported, but the path isn't calculated from distance in this example.
Finding the best route through a series of stops follows the same workflow as other network analyses.
Network analysis workflow
Whether you are performing a route, service area, or other network analysis in the ArcGIS Network Analyst extension, the workflow is similar. This topic presents the general procedure for solving network problems.
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 environment.
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.
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.
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.
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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.