Maptitude Help / Geographic Analysis Tools / Facility Location

Solving a Facility Location Problem

Facility Location Models are used to identify good locations for warehouses, hospitals, retail stores, manufacturing facilities, and other types of facilities. In general, the goal in locating such facilities is either to provide a high level of service or to minimize operating costs.

Facility location problems involve choosing the best location for one or more facilities from a set of possible locations. Here are two examples:

• You need to determine the best location for a new branch of a public library. Your goal is to provide the best overall level of access to city residents.
• You need to determine the best location for a new police station. Your goal is to reduce the maximum distance a patrol car needs to travel from the station to a resident’s home.

The goal of a facility location problem may be to determine the number of facilities that are required to guarantee a prescribed level of service. For example:

• You want to locate fire stations so that every building in a city is within five minutes of a station
• You need to locate voting stations so that the average resident is less than two miles away from the nearest one

There are also facility location problems where the goal is to maximize the distance between facilities and the population they serve. Landfills and power plants, for example, are often located relatively far from major population centers.

A final complication in facility location problems involves the presence of existing facilities. The locations of these facilities obviously affect the choice of locations for new facilities. In addition, a common situation involves both adding new facilities and closing one or more existing facilities.

Issues in Facility Location

In a facility location problem, the goal is to locate one or more facilities. The locations for these facilities are chosen from a set of candidate locations. In a regional warehouse location problem, for example, you may have identified half a dozen parcels that you can acquire for a new facility; in a nationwide location problem you may have chosen 25 metropolitan areas as possible facility sites. Typically, there is also a set of existing facilities to be considered in evaluating new locations.

Each facility serves a number of clients. In some cases (e.g. library or polling place) the clients are individuals or households, while in other cases (e.g. warehouse) the clients are stores or manufacturing facilities that are served by the facility. In some cases a client may require more deliveries than another client located the same distance away. In this situation, you can apply a weight to apply more importance to the clients who require more deliveries.

Sometimes you may want to consider closing existing facilities as part of a facility location problem. In this case, you treat the facilities that might be closed as candidate facilities rather than as existing facilities. The procedure then determines whether these facilities should be closed or kept in operation.

Solving the Facility Location Problem

Facility Location Inputs

The data for a facility location problem consist of:

• A point or area layer of client locations. The client layer can contain an optional weighting field.
• A point or area layer containing the candidate facility locations. If there are existing facilities to be considered, you must make separate selection sets of the candidate and existing facilities. The same features cannot appear in both of these selection sets. Existing locations that you are considering closing should be in the candidate set.

NOTE: Maptitude has a default limit of 30,000 routes between clients and facilities. Values above 30,000 may fail depending on your computer's available memory. You can change the number of allowed facility location routes by choosing Edit>Preferences and changing the facility location route limit on the Routing tab. See Edit Preferences for more information.

Facility Location Optimization Options

To solve a facility location problem, you must choose your objective. In general, the goal of a facility location problem is one of the following:

• Provide the best overall level of service to clients, without worrying about whether service to any particular client is much worse than average
• Provide the best possible service to the client who is farthest away from the set of facilities; often used for emergency services
• Keep facilities away from clients by placing the facilities as far as possible from the nearest client; often used for facilities that are considered to be undesirable, such as landfills or incinerators

You can either indicate the number of facilities you want to locate or allow Maptitude to determine the number that is required to meet a specific objective. When you have Maptitude determine the number of facilities, you choose whether to base the limit on an average time or distance to maintain for the serviced clients or on a maximum acceptable time or distance to service a client. Maptitude will find the smallest number of facilities to open to satisfy the criteria that you chose.

Facility Location Results

There are two primary outputs from the facility location procedure:

• A selection set of the locations of the new facilities. This selection set is always a subset of the features that were included in the candidate location set, and is automatically displayed on the map.
• A table that contains one record for each client that indicates the facility to which each one is assigned and the time/distance from that client to its assigned facility. If a weighting field was applied to the client set, the client assignment table will contain a weighted time/distance equal to the time/distance multiplied by the value in the weighting field. This table is automatically joined to the client layer and displayed in a dataview. It can be used to create thematic maps illustrating the assignment of clients to facilities.

For a video tutorial see: (Internet connection required) • Solving a Facility Location Problem

To Solve the Facility Location Problem

1. Open a map that contains a point or area layer of clients and a point or area layer of candidate facility locations. If the facility layer contains any existing sites, create selections separate selections sets of the existing and candidate facilities.
2. Choose Tools>Analysis>Facility Location or click  Facility Location in the analysis tools drop-down on the Standard toolbar to open the Facility Location wizard and make choices as follows:

3. Click Next and make facility choices as follows:

4. Click Next and make choices as follows:

5. Click Next and choose the number of new facilities as follows:

6. Click Next and choose how you want to optimize the new facilities.

If you chose the Manual option in the previous step, make choices as follows:

If you chose the Automatic option in the previous step, make choices as follows:

7. Click Finish.

Maptitude determines the best facility location(s) from the candidates, creates a selection set of those locations, and highlights them on the map. Maptitude also opens a dataview of the facility assignment table joined to the client layer.

 

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