Flow maps
The main purpose of a flow map is to show the flow of a particular phenomena. In this lab we created two examples of flow maps: radial flow and network flow. The first part of this was about learning how to use ArcGIS to map radial flow. A map of the amount of mail transported between different airports in the USA was created (figure 8). The main data source for this map was data from the Federal Aviation Administration. In addition to the mail traffic map, a map with passengers between those airports was created (figure 9). The result of the map shows that mail volumes on board on airplanes are greatest between Alaska and the other states of America. By using different width for lines, the different volumes are easy to see. Next to the high traffic volumes to and from Alaska, there is a lot of traffic between the so-called Network Distribution Centers. The dataset contained a lot of flights were the passengers and mail was equal to 0. These flight were deleted from the dataset because it is not the purpose to map the flights without mail or passengers.

     Figure 8. On flight market mail enplaned
 
      Figure 9. On-flight market passengers enplaned

Network flow maps are used to display the flow of some feature through a network. In this Lab we made a network flow map of traffic flow in the state of Oregon. Data source for this lab was traffic flow data from the Oregon Department of Transportation. By using different line widths it was easy to display the amount of traffic flow a highway or interstate has on a daily basis. To keep some structure in the map, a distinction between interstates and highways was made (figure 10).  The result of the map shows that traffic flow is greatest around the bigger cities (Portland, Salem, Medford).
    Figure 10. Network flow in the state of Oregon