Available with Network Analyst license.
Descriptors are attributes that describe characteristics of the network or its elements. Unlike costs, descriptors are not apportioned. This means that the value does not depend on the length of the edge element. For example, the number of lanes is an example of a descriptor on a street network. Speed limits of streets is another descriptor attribute for a street network. Although it is not a cost attribute and cannot be used as an impedance, it can be used in conjunction with distance to create a cost attribute (for example, drive time) that can be used as an impedance.
Properties
The Descriptors tab displays the descriptor attributes that are available with the network dataset and the properties associated with the selected descriptor.
The Properties section displays how the selected descriptor is configured. It lists the metadata associated with the descriptor attributes and the details on how the parameters and evaluators are configured.
The following are the descriptor attribute properties:
- Name—The name of the descriptor attribute.
- Units—The units of the descriptor attribute. The descriptor attribute can be time, distance, or speed based. You can also choose Other if the unit is not specified.
- Data Type—The data type of the descriptor attribute. You can choose integer, float, double, or bool.
- Parameters—These are placeholders for values that you can change for a particular analysis. They each have a meaningful default value that can be overridden when necessary.
- Evaluators—Each attribute defined in the network must provide values for each source and direction (along and against for edges) participating in the network. An evaluator assigns values for the attribute of each source and travel direction, and a default evaluator for each element is used for those sources and directions that do not have an assigned evaluator for an attribute.
Note:
The best practice for editing network attributes in a network dataset is to edit them in a project that does not include layers that use the network dataset. Some editing may be blocked on the network dataset properties dialog box if there are layers in the project that use this network dataset. It is recommended that you create a blank project, add a connection to the geodatabase that contains the network dataset, and make edits in this project. When the layers using this network dataset are opened in an ArcGIS AllSource session, you won't be able to add, delete, or rename a cost or a restriction attribute. This is to ensure that the network dataset schema updates succeed and that the layers using it are initialized properly when opened.
Note:
When you change any network attributes, you must build the network dataset to reestablish the connectivity, recalculate affected attributes, and update the network elements.
Create a descriptor attribute
Complete the following steps to create a descriptor attribute:
- Access network attributes on the Network Dataset Properties dialog box.
- Click the Descriptors tab.
- Click the Options button
in the upper right corner of the dialog box. - Click the New button
from the menu, or press Ctrl+N.A new row is added to the Descriptor section.
- In the Properties section, type the name for the new descriptor attribute in the Name field.
- Choose a unit from the Units drop-down list. If the descriptor attribute is time based, choose any of the available time units. If the descriptor attribute is distance based, choose a distance-based unit. If the descriptor attribute is speed based, choose a speed-based unit. Otherwise, choose Other.
- Expand the Parameters section, if necessary, to add a new parameter.
- In the Evaluators section, assign an evaluator to the source features.
- Click OK.
The descriptor attribute is saved to the network dataset.
Copy a descriptor attribute
Complete the following steps to make a copy of the selected descriptor attribute:
- Access network attributes on the Network Dataset Properties dialog box.
- Click the Descriptors tab.
- Choose a descriptor attribute to copy.
- Click the Options button in the upper right corner of the dialog box.
- Click the Copy button
, or press Ctrl+Shift+N.A copy of the selected descriptor attribute is created, and a new row with the similar descriptor name is added. (For example, if you copy a descriptor attribute named RoadClass, a new descriptor attribute with the name RoadClass 2 will be added.) All the properties for this new descriptor attribute are inherited from the one you copied.
- Click OK to save the changes to the network dataset.
Delete a descriptor attribute
Complete the following steps to delete a descriptor:
- Access network attributes on the Network Dataset Properties dialog box.
- On the Descriptors tab, select the descriptor attribute to delete.
- Click the Options button in the upper right corner of the dialog box.
- Click the Delete button
, or press Ctrl+D.The selected descriptor attribute is deleted.
Note:
If the descriptor attribute is used by other travel modes or attributes, the Delete option is unavailable. To access the Delete button, remove the selected descriptor attribute from all travel modes and attributes.Edit a descriptor attribute
Complete the following steps to change the properties or other attributes related to the descriptor attribute:
- Access network attributes on the Network Dataset Properties dialog box.
- Click the Descriptors tab.
- Choose a descriptor attribute to edit.
- In the Properties section, make necessary edits to the Name, Units, and Data Type properties.
- Edit the parameters associated with the descriptor attribute if necessary.
- Edit the evaluators of the descriptor attribute if necessary.