Introducing Geographic Information Systems with ArcGIS: A Workbook Approach to Learning GIS, 3rd Edition

Linear Referencing

STEP-BY-STEP

The first concept to grasp is that of a “route.” A route is a linear feature, probably made up of several or many other linear features. A route has a unique identifier and has a measurement system stored with its geometry.

Exercise 9-5 (Project)

Experimenting within Linear Features

____ 1. Start ArcCatalog. In the Catalog Tree find the folder

[___] IGIS-Arc\Linear_Referencing.

Copy it into ___ IGIS-Arc_YourInitials.

____ 2. In

___IGIS-Arc_YourInitials\Linear_Referencing

\Pittsburgh.mdb\PITT_Roads_Routes

preview the Geography of Just_Roads. Using the Identify tool, click on a few features. You will notice that you that you get some standard information (e.g., feature name) and also a route identifier (called ROUTE1), a beginning mile point, and an ending mile point. Look at the attribute table of Just_Roads. How many road segments are there? ________.

____ 3. In the Catalog Tree, click All_Routes. Switch back to the Geography display, which thins out a lot compared to Just_Roads. These are road features that have been combined and designated as “routes”—all under the name of ROUTE1. Each route is composed of sets of features from Just_Roads.

____ 4. Again use Identify. Notice that you get completely different results from those you got before. The shape is still polyline, but the Shape_Length is much longer. When you click on a feature, the line that flashed is usually lengthy—composed of many of the features you saw before. Look at ...