WMS:Assigning Equation to Arcs

The primary attribute for a time computation arc is the equation that will be used to compute travel time for the flow path segment represented by the arc. In addition to the equation, the length, slope, and travel time for the arc are also stored. Length is defaulted from the length of the arc and a slope will be determined for the arc if there is an underlying TIN or DEM. However, you can edit either of these values if you want. For example you may decide that the actual flow path is somewhat more sinuous than the arc represents and decide to increase the length. The equation and appropriate variables are defined for an arc using the Time Computation Arcs Attributes dialog shown below.

This dialog is used to set all values and compute travel times for selected arcs. It can be accessed by selecting an arc and then choosing the Attributes command from the Feature Objects menu in the Map module, by double clicking on the arc when in the map module, or when using the Travel Time Computation dialog. If multiple arcs are selected the ArcID window displays the ID of all selected arcs and you may edit the equations / variables of any selected arc by choosing it from this window. While the selected arc is highlighted in the Graphics Window, you may find it useful to toggle on the display of arc IDs from the Feature Object Display Options dialog.

When using the Time Computation Arc Attributes dialog the Instructions / Results window will let you know which variables need to be entered before a time computation can be made, and when all variables are defined it will display the computed travel time of the selected arc.

Related Topics

• Travel Times from Map Data
• Editing Equation Variables
• Time Computation Coverage