Network and Service Area Delineation

 

Introduction

 

You will learn how to build a transportation network and use it to delineate service areas in ArcGIS. A network is a system of interconnected elements. Connectivity is inherently important in order to travel over the network. Network elements, such as edges (lines) and junctions (points), must be interconnected to allow navigation over the network. Additionally, these elements have properties (e.g., cost and turns) that control navigation on the network. In ArcGIS, network is a special dataset built on polyline features (e.g., streets). Once the network dataset is created, users can use it to do various network analyses, such as routing, service area delineation, find closest facilities, etc.

 

Instructions

 

You will use Exercise 8’s street feature class (SFStreets) to build the network for delineating the service areas of the two existing Better Books’ stores. The sample data are available in the I:\Students\Instructors\Geoffrey_Duh\GISMarketing\BetterBooksSF folder. Copy these data to your working folder in C:\Users before you continue.

 

A. Creating a network dataset

 

  1. Add SFStreets to ArcMap and view its attribute table. Pay special attention to Shape_Length and SPEED_MPH fields. Make sure you know the units of these attributes.

 

Field

Unit

Shape_Length

 

SPEED_MPH

 

 

  1. To replicate the analysis done in Exercise 8, we need to calculate the travel time in minutes for each street segment. Add a new field, named MINUTES with double as data type, to the attribute table of SFStreets. Use the field calculator and the formula below to update the values in MINUTES field. Note that you only need to construct the right side of the equation in the calculator.

 

MINUTES = Shape_Length * 0.0006213712 / SPEED_MPH * 60

 

  1. Now open ArcCatalog and navigate to the BetterBooksSF.mdb. Since you can only create a transportation network in a Feature Dataset, you need to create one and import the streets feature class to the dataset. Right-click the mdb and select new, then select Feature Dataset. Type a name (e.g., StreetNetwork) and click Next. In the next dialog, click Import and select the SFStreets feature class to use its coordinate system information to define the new feature dataset. Click Next and Finish to complete the process.

 

  1. Right click on the Feature Dataset you just created and select Import/Feature Class (single) to import the SFStreets feature class into the feature dataset. Call the output feature class “Streets.” When done, you can click the plus (+) sign of the feature dataset to reveal its content.

 

  1. Right click on the Feature Dataset and select New/Network Dataset. Click Next to accept the default name. Make sure the Streets feature class is checked and click Next to continue. Click Next to bypass the connectivity setting. Select No to indicate that you don’t want to modify the connectivity with elevation field data. Select No for not modeling turns of the network. Next dialog will list MINUTES as the network attribute. You can add other attribute to define transportation cost. Here we just select Next to continue. Select No in the next dialog and click Next to view a summary of the parameters. Click Finish and select Yes to build the network. Click Close to ignore the error message. The error was caused by the same error you encountered when calculating the Minutes attribute.

 

  1. Take a look at the Feature Dataset and its content. Close ArcCatalog when done.

 

B. Delineating service areas

 

  1. Add the network dataset to ArcMap and answer Yes to add all feature classes participated in the network. Add the BBStores feature class to ArcMap.

 

  1. Make sure you have turned on the Network Analyst extension and open the Network Analyst toolbar in ArcMap. The network you created should be listed in the Network Dataset field.

 

  1. Now, select New Service Area from the Network Analyst menu. Use the Load Locations function to load the two store locations as facilities’ locations. Click the Service Area Properties icon to open the Layer Properties dialog. Go to the Analysis Settings tab and change the default breaks to 1 (minute) and solve network analysis. Repeat the analysis with default breaks set to 3 (minutes).

 

  1. Compare the results with the BBDriveTimeMA feature class that you used in exercise 8.