Resources Allocation

The resources allocation is a function that identifies an influence zone of a center or a point object. This center, source or receptor, has a demand value associated. This demand value might correspond, for instance, to the total power that an electrical substation can afford, or a number of students that can go to a certain school.

For this type of application, the parameters that have to be modeled in the network are the following:

    1. The center has to correspond to a point object and has an attribute that can be used as a demand (application dependent).
    2. Each linear representation has to have a demand value associated, which is equivalent to the center demand. This demand value can be obtained from an object attribute for each linear representation.
    3. As in the shortest path application, the flow directions in the network must be modeled. These flows are specified by the positive (from the initial node) impedances (costs) and negative ones (from the final node). Impedance values equals to -1 indicate a blocking in the respective direction. The impedance can be modeled using its own lines distance or any object attribute.

The resources allocation can be computed from the reference object, in this cases the flow directions considered are the ones that come from the source. For instance, the electrical power produced in an electrical power plant is distributed to the consumers through a network. The electrical power plant is the center and concentrates the available energy. The consumers, located throughout the network, creates a demand to be allocated. In this case, the resource available, electrical power, has to be transported through the network, starting in the power plant, to satisfy the consumers demand.

In another situation the flow directions considered has to be the ones arriving to the center. As an example, imagine the students situation, they live throughout a streets network and they have to move towards the school. The school has a total capacity, which works as a demand, and the demands of each linear element in the network corresponds to the number of students in each part.

In the network modeling the impedance item is fundamental. Impedance is the cost for moving around the network. In the school example, the impedance could be the time that the student spent to arrive in the school. Each linear element in the network has impedances associated in both of the flow directions.

Executing a resource allocation:

  • activate the IL of the network model in the "Control Panel";
  • verify if the Current Infolayer's name corresponds to the active layer in the Object area:
    • click on Select... to select the point object in the window. The objects name selected is then presented in the Name field and the object attributes listed in Demand Attributes. Click over a demand attribute and its value is presented in the Demand field. The selected attribute has to be of the numerical type.
    • click on Allocate: and select between Arriving Node or Leaving Node to the considered flow direction. In the school example it would be "Arriving Node", because the students move towards the school. In the electrical power plant case serving consumers in the network, the "Leaving Nodes" should be selected.
  • in the Network Parameters Cost area:
    • click on Impedance if one wants or not to have the impedance values computed again. If the processing is repeated and the cost values are the same, this item can be unmarked, forcing the system to use the data stored in the database without computing them again.
    • select if the impedance will be an Object Attribute or a Distance among the nodes in the network. Notice that in the distance case, the attributes list of the impedance stay deactivated;
    • type the Maximum Impedance value. The program ends when the maximum impedance is reached or when the demand parameter of the selected center is reached;
    • choose in the category list the one that belongs to the linear objects that are represented in the network;
  • Select the impedance attribute to be used;
  • Activate or deactivate the demand attribute for each linear element. Select the demand attribute of the linear elements . - Press the Apply button. - The "Description" button lists the obtained results.

See also:

Digitalization of Maps