1. Network and Dynamic Segmentation Chapter 16

2. Introduction A network consists of connected linear features. Dynamic segmentation is a data model that is built upon lines of a network and allows the use of real-world coordinates with linear measures such as mileposts. Both models must have the appropriate attributes for real-world applications.

3. Introduction ARC/INFO can work with both network and dynamic segmentation ArcView with Network Analyst can do network model

4. Network A network is a line coverage, which is topology-based and has the appropriate attributes for the flow of objects such as traffic. Examples: links, turns, one-way streets, overpass, underpass; impedance

5. Link Impedance Link impedance: measure of the cost of traversing a link; cost rather than length, such as travel time (30 vs 10 mph). Directional differences (to-from node) Time of day Day of week

6. Turn Impedance Transition from one arc to another Time to make the turn Turn table because of changing conditions; node number, arc numbers, turn impedance Straight, left, right, possibly U Usually directional Negative impedance for prohibited activity

7. Putting Together a Street Network Preliminary coverage from TIGER, convert to real world coordinates. Edit and update: attributes, new/changed streets, pseudo nodes for attributes change. Add impedance values. Consistent one-way streets and directions Create turn table

8. Network Applications Shortest Path Analysis path with minimum cumulative impedance between nodes in-vehicle Route Guidance System (RGS) Traveling salesman problem more complex must visit each one time must return to original stop Many algorighms

9. Network Applications Shortest Path Analysis ARC/INFO has PATH and TOUR ArcView Network Analyst has “Find Best Route” Both create a route and option of providing directions

10. Network Applications Closest Facility Computes shortest paths from the selected location to all candidate facilities and then chooses the closest facility

11. Network Applications Allocation Study of spatial distribution of resources through a network Often refer to public facilities service zones Efficiency is response time Location-Allocation Minimize use of resources using facilities and at the same time meeting objectives

12. Network Applications Maximum covering model maximizes the demand covered within a specified time or distance. Urban Transportation Planning Model typically uses four-step process of trip generation, trip distribution, modal choice, and trip assignment complex, must have arc-node topology

13. Dynamic Segmentation Built upon arcs of a network Basic elements of routes, sections, and events Route is a collection of sections and resides in a line coverage as a subclass Section refers directly to arcs in the line coverage and provides measures to route system Events are occurrences related to the route system

14. Creating Routes On new arcs On existing Arcs Different types of routes simple (one direction without loop or branch) combined (route is joined by another route) split route (route subdivides into two routes) looping route (route intersects itself)

15. Event Tables Events are attribute data measured on a linear reference system point events, such as accidents and stop signs continuous events, such as speed limits (always present) linear events, such as pavement conditions (off and on situations)

16. Applications of Dynamic Segmentation Display, query, and analysis of routes, measures, and events. Analysis of accidents Changes