Loading the Demand Points into the Model
As you will recall from the lecture videos, Modeling Network Paths, the demand points are places served by the facility in some way. The exact nature of the demand points will depend on the service being provided. In this scenario, the history of incident responses serves as demand points for the proposed fire stations. The demand points have attributes that influence cost or place limitations on the model. In this model, the demand points need to be weighted so that certain types of incidents will have a higher priority. By default, each demand point has a value of 1 for weight. When determining which fire station will be chosen, the weights for all of the demand points within its time window cutoff are summed. The sum of the weights is called allocated weight. It represents the total demand allocated to the chosen facility. However, you will change the weights of certain types of calls by adding a weight field to the attribute table then populating the results with the following weights:
- Assign a weight of 3 for incidents involving building fires, wildland fires, brush fire, and trash fires. In the incident history attribute table, the incident types are 111, 141, 142, and 151.
- Assign a weight of 2 for incidents involving medical assistance and emergency medical services. In the incident history attribute table, the incident types are 311 and 3211.
- Assign all other incident types a value of 1.
Start by adding a Weight field to the incident history layer. Use an attribute selection to select the records for each incident type. Then use the Field Calculator to populate weight value for the selected records. If you will recall from previous courses, you can access Field Calculator by right-clicking on the field name, Weight. Once the demand points are assigned the appropriate weights, you are ready to load them into the model. Right-click on Demand Points in the Network Analyst Window and select Load Locations. From the drop-down menu next to Load From, select the incident history layer. Facility parameters are defined under the Location Analysis Properties pane using two attributes, Field, and Default Value. If the layer does not have a field that matches the property, a default value may be entered instead.
Use the following values in the Location Analysis Properties. Keep the default values for any properties not listed here.
|CurbApproach||Either side of vehicle|
Once the values above are entered, click OK.