3D Analyst Tools ArcToolbox

Make Location-Allocation Layer Tools

How to use Make Location-Allocation Layer Tool in Arc Toolbox ArcMap ArcGIS??

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Make Location-Allocation Layer Tool, Analysis Toolset, Network Analyst Tools Toolbox

 

Make Location-Allocation Layer

Makes a location-allocation network analysis layer and sets its analysis properties. A location-allocation analysis layer is useful for choosing a given number of facilities from a set of potential locations such that a demand will be allocated to facilities in an optimal and efficient manner.

1.    Input Analysis Network

The network dataset on which the location-allocation analysis will be performed.

2.    Output Layer Name

Name of the location-allocation network analysis layer to create.

3.    Impedance Attribute

The cost attribute to be used as impedance in the analysis.

4.    Travel From (optional)

Specifies the direction of travel between facilities and demand points when calculating the network costs.

1. FACILITY_TO_DEMAND—Direction of travel is from facilities to demand points. Fire departments commonly use the this setting, since they are concerned with the time it takes to travel from the fire station to the location of the emergency.
2. DEMAND_TO_FACILITY—Direction of travel is from demand points to facilities. Retail stores commonly use this setting, since they are concerned with the time it takes the shoppers to reach the store.

Using this option can affect the allocation of the demand points to the facilities on a network with one-way restrictions and different impedances based on direction of travel. For instance, a facility may be a 15-minute drive from the demand point to the facility, but only a 10-minute trip when traveling from the facility to the demand point.

5.    Location-Allocation Problem Type (optional)

The problem type that will be solved. The choice of the problem type depends on the kind of facility being located. Different kinds of facilities have different priorities and constraints.

1. MINIMIZE_IMPEDANCE—This option solves the warehouse location problem. It selects a set of facilities such that the total sum of weighted impedances (demand at a location times the impedance to the closest facility) is minimized. This problem type is often known as the P-Median problem.
2. MAXIMIZE_COVERAGE—This option solves the fire station location problem. It chooses facilities such that all or the greatest amount of demand is within a specified impedance cutoff.
3. MAXIMIZE_CAPACITATED_COVERAGE—This option solves the location problem where facilities have a finite capacity. It chooses facilities such that all or the greatest amount of demand can be served without exceeding the capacity of any facility. In addition to honoring capacity, it selects facilities such that the total sum of weighted impedance (demand allocated to a facility multiplied by the impedance to or from the facility) is minimized.
4. MINIMIZE_FACILITIES—This option solves the fire station location problem. It chooses the minimum number of facilities needed to cover all or the greatest amount of demand within a specified impedance cutoff.
5. MAXIMIZE_ATTENDANCE—This option solves the neighborhood store location problem where the proportion of demand allocated to the nearest chosen facility falls with increasing distance. The set of facilities that maximize the total allocated demand is chosen. Demand further than the specified impedance cutoff does not affect the chosen set of facilities.
6. MAXIMIZE_MARKET_SHARE—This option solves the competitive facility location problem. It chooses facilities to maximize market share in the presence of competitive facilities. Gravity model concepts are used to determine the proportion of demand allocated to each facility. The set of facilities that maximizes the total allocated demand is chosen.
7. TARGET_MARKET_SHARE—This option solves the competitive facility location problem. It chooses facilities to reach a specified target market share in the presence of competitive facilities. Gravity model concepts are used to determine the proportion of demand allocated to each facility. The minimum number of facilities needed to reach the specified target market share is chosen.

6.    Number of Facilities to Find (optional)

Specifies the number of facilities that the solver should locate.

The facilities with a FacilityType value of Required are always part of the solution when there are more facilities to find than required facilities; any excess facilities to choose are picked from candidate facilities.

Any facilities that have a FacilityType value of Chosen before solving are treated as candidate facilities at solve time.

The parameter value is not considered for the Minimize facilities problem type since the solver determines the minimum number of facilities to locate to maximize coverage.

The parameter value is overridden for the Target market share problem type because the solver searches for the minimum number of facilities required to capture the specified market share.

7.    Impedance Cutoff (optional)

Impedance Cutoff specifies the maximum impedance at which a demand point can be allocated to a facility. The maximum impedance is measured by the least-cost path along the network. If a demand point is outside the cutoff, it is left unallocated. This property might be used to model the maximum distance that people are willing to travel to visit your stores or the maximum time that is permitted for a fire department to reach anyone in the community.

Demand points have a Cutoff_[Impedance] property, which, if set, overrides the Impedance Cutoff property of the analysis layer. You might find that people in rural areas are willing to travel up to 10 miles to reach a facility, while urbanites are only willing to travel up to 2 miles. You can model this behavior by setting the impedance cutoff value of the analysis layer to 10 and setting the Cutoff_Miles value of the demand points in urban areas to 2.

8.    Impedance Transformation (optional)

This sets the equation for transforming the network cost between facilities and demand points. This property, coupled with the Impedance Parameter, specifies how severely the network impedance between facilities and demand points influences the solver's choice of facilities.

1. LINEAR—The transformed network impedance between the facility and the demand point is the same as the shortest-path network impedance between them. With this option, the impedance parameter is always set to one. This is the default.
2. POWER—The transformed network impedance between the facility and the demand point is equal to the shortest-path network impedance raised to the power specified by the impedance parameter. Use this option with a positive impedance parameter to specify higher weight to nearby facilities.
3. EXPONENTIAL —The transformed network impedance between the facility and the demand point is equal to the mathematical constant e raised to the power specified by the shortest-path network impedance multiplied with the impedance parameter. Use this option with a positive impedance parameter to specify a very high weight to nearby facilities.Exponential transformations are commonly used in conjunction with an impedance cutoff.

Demand points have an ImpedanceTransformation property, which, if set, overrides the Impedance Transformation property of the analysis layer. You might determine the impedance transformation should be different for urban and rural residents. You can model this by setting the impedance transformation for the analysis layer to match that of rural residents and setting the impedance transformation for the demand points in urban areas to match that of urbanites.

9.    Impedance Parameter (optional)

Provides a parameter value to the equations specified in the Impedance transformation parameter. The parameter value is ignored when the impedance transformation is of type Linear. For Power and Exponential impedance transformations, the value should be nonzero.

Demand points have an ImpedanceParameter property, which, if set, overrides the Impedance Parameter property of the analysis layer. You might determine that the impedance parameter should be different for urban and rural residents. You can model this by setting the impedance transformation for the analysis layer to match that of rural residents and setting the impedance transformation for the demand points in urban areas to match that of urbanites.

10. Target Market Share (optional)

Specifies the target market share in percentage to solve for when the Location-Allocation Problem Type parameter is set to Target market share. It is the percentage of the total demand weight that you want your solution facilities to capture. The solver chooses the minimum number of facilities required to capture the target market share specified by this numeric value.

11. Default Capacity (optional)

Specifies the default capacity of facilities when the Location-Allocation Problem Type parameter is set to Maximize capacitated coverage. This parameter is ignored for all other problem types.

Facilities have a Capacity property, which, if set to a nonnull value, overrides the Default Capacity parameter for that facility.

12. Start Time (optional)

Indicates the time and date of departure. The departure time can be from facilities or demand points, depending on whether travel is from demand to facility or facility to demand.

If you have chosen a traffic-based impedance attribute, the solution will be generated given dynamic traffic conditions at the time of day specified here. A date and time can be specified as 5/14/2012 10:30 AM.

Instead of using a particular date, a day of the week can be specified using the following dates:

1. Today—12/30/1899
2. Sunday—12/31/1899
3. Monday—1/1/1900
4. Tuesday—1/2/1900
5. Wednesday—1/3/1900
6. Thursday—1/4/1900
7. Friday—1/5/1900
8. Saturday—1/6/1900

For example, to specify that travel should begin at 5:00 p.m. on Tuesday, specify the parameter value as 1/2/1900 5:00 PM.

13. Accumulators
14. Hierarchy
15. Output Option
16. Restrictions

No. 13, 14, 15 and 16 were explained in a previous tool to understand these categories. Click here to access a tool in which these categories are explained.