Designing the network dataset
To model transportation networks, a network dataset must be thoughtfully designed. You can achieve this by following the four-step process discussed below.
Step 1: Select the source workspace
A network dataset can be created within a geodatabase or shapefile workspace, or it can reside in an ArcGIS StreetMap dataset. A shapefile network dataset supports one edge source, while a geodatabase network supports multiple edge and junction sources. An ArcGIS StreetMap dataset is a highly compressed countrywide street network that can be used for network analysis.
- If you want to model multimodal networks, create your network dataset in a geodatabase workspace. If you have multiple sources that connect to each other using sophisticated connectivity rules, the network dataset should be created in a geodatabase workspace.
- If you have a single edge source in shapefile format that you want to use for quick and simple network analysis, create a shapefile network dataset.
- If you have ArcGIS StreetMap data, you can use it directly for network analysis.
Step 2: Identify the sources and the role they will play in the network
- A shapefile network dataset is composed of an edge source and an optional turn source. Geodatabase feature classes that are present in the same feature dataset as the network can participate as sources in the network. It is, therefore, important to identify which of those will participate as network sources.
- If the network dataset supports turns, the turn feature class or classes that will be used need to be identified. If your turns are stored as ARC/INFO or ArcView GIS turn tables, you can migrate your turn data to turn feature classes.
Step 3: Model connectivity
Connectivity can be established for a network dataset using the ArcGIS Connectivity model in conjunction with the elevation field model.
- It is important to study the network and determine how the different elements will connect to each other.
- You should design your connectivity concept before creating a network dataset.
- A multimodal network requires multiple connectivity groups and the presence of transfer junctions in each connectivity group.
- The elevation field model can be used to enhance the connectivity of the network, if there is elevation field data available.
- For each edge and junction source, determine the connectivity policy.
- Address special scenarios, such as bridges and tunnels.
Step 4: Define attributes and determine their values
- Identify the impedances to be used during network analysis and determine their values from network sources.
- Determine the restrictions that will be used to control navigation over the network.
- Establish hierarchy (if required) for the edge elements in the network.