What are network analysis layers?
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.
Network analysis layers in ArcMap
The active network analysis layer in ArcMap is displayed in the Network Analyst window. The name is shown in the drop-down list. The network analysis classes and objects are displayed in the pane below the list.
Network analysis layers are displayed in the ArcMap table of contents as composite layers.
Network analysis layers are bound to network datasets
Network analyses are always performed on network datasets. Consequently, a network analysis layer must be bound to a network dataset. The binding is made by a link that points to the location of the associated network dataset in the file system.
Note that a network analysis layer doesn't contain a network dataset; it simply points to a network dataset.
If you make a network analysis layer using a geoprocessing tool, you set the related network dataset as a tool parameter. In ArcMap, a network dataset must be added before a network analysis layer can be created. When an analysis layer is created, ArcGIS Network Analyst binds it to the active network dataset.
The active network dataset is displayed in ArcMap on the Network Dataset drop-down list, which is on the Network Analyst toolbar.
Network analysis layer properties
The network analysis layer has its own properties, even though it is a composite layer made up of subordinate feature layers that in turn have their own sets of properties. Some of the network analysis layer properties are crucial to defining the analysis you want to perform. Properties include the impedance to be used and the restrictions to be obeyed, as well as the U-turn policy, output shape type, accumulation attributes, and properties for finding network locations. Additionally, each kind of analysis has specific properties of its own.
The properties for performing an analysis are set on the analysis layer's dialog box.