2011

Table Of Contents

linked external database column. The expression will be evaluated for

each link. Click (Expression Evaluator) to select data from a list.

■ Link Direction — Specify a direction for the trace. If you leave the

box blank, bi-directional (0) is used.

■ Reverse — Select this option to use the reverse of the direction

indicated in the Link Direction box.

■ Link Direct Resistance — Specify the resistance to travel in the

direction that a link was created. If you leave the box blank, the length

of the line (.LENGTH) is used.

■ Link Reverse Resistance — Specify the resistance in the opposite

direction along a link. If you leave the box blank, the length of the

line (.LENGTH) is used.

■ Node Resistance — Specify the resistance to cross the node, for

example, resistance for a valve in a pipe network, or a junction in a

road network. If you leave the box blank, zero (0) is used.

■ Maximum Resistance and Minimum Resistance — Any path that has

a total resistance below the minimum or above the maximum is

ignored.

For example, if you stored the average speed limit for a link (in miles per

hour) in an object data table called street_data, you could find the fastest

route between two points by entering the expression (/ .length (*

:speed@street_data 5280) which divides the length of each link by the

average speed per foot (where 5280 is the number of feet in a mile).

9 Click Next.

10 In the Network Topology Analysis - Output dialog box, indicate whether

or not to view the results of the trace onscreen and whether to save the

trace results as a new topology.

■ To view your shortest path trace onscreen, select Highlight. Choose

a highlight color from the Color list.

You should use a highlight color that is different from the color of

the objects in your map.

■ To save the shortest path trace as a new topology, select Create

Topology. Enter a name and description for the new topology. The

new topology will be created on the existing objects.

11 Click Finish to perform the shortest path trace.

Performing a Shortest Path Trace | 1327