Redistricting in the Computer Age: A Review of Maptitude for Redistricting

By Mekonnen Gessesse

Vol. 22, No. 4, 2000 p. 29

Gone are the days when paper, map markers, and desk calculators were used to draw redistricting plans. By the 1990s, personal computer or PC-based mapping became widespread. Geographic Information System (GIS) technology has combined hardware, software, and data to analyze and display spatial information on a computer screen that is easy to understand and manipulate. The PC-based GIS programs were introduced when the encoded geographic data known as the TIGER (Topologically Integrated Geographic Encoding and Referencing) system was introduced on CD-ROM disks providing easy access via DOS and Windows.

GIS is used to analyze the location and shape of geographic features, create buffers around a feature, define areas of influence, and create districts or territories by combining smaller areas together.

There are many GIS programs available, but few can handle redistricting. Of these, ARCInfo, Arch View GIS, and GIS Plus are the most important. Many state legislative offices and community organizations, including the Southern Regional Council, have extensively used GIS Plus, a program developed by Caliper Corporation. As computer technology improved, GIS Plus was updated to a more advanced program called Maptitude for Redistricting. Maptitude easily translates the Census Bureau Geographic file (TIGER/Line file) into a manageable format. Its function, to create maps showing the distribution of population by race, is very impressive, as is its ability to create districts by aggregating smaller geographic layers such as blocks and precincts thereby producing different reports of newly-created districts.

Once a map is created from the TIGER/Line file, it can be saved as a working file and modified using Windows-based pull-down menus and tool bars. It's easy to change line width and colors, or the color of any map feature. It is also possible to display more than one geographic layer on the same map. For example, blocks can be shown overlaid by streets and voting tabulation districts (VTD's).

Maptitude's capacity to query and display data on maps is one of its strongest features. Thematic maps can be easily created. For example, black population percentages can be displayed by varying colors of blocks. The address-matching tool helps locate point locations such as addresses of incumbents, or any other features whose street and zip code addresses are available.

There are several phases of redistricting mapmaking: calculating the ideal population, aggregating polygons to build a district, automatically computing values to reveal the district's characteristics; and finally, producing maps and reports. Maptitude's GIS program has a module with its own toolboxes for districting and redistricting functions that lets the user create a plan using any level of base geography with a designated control field (e.g. total population), a target value (ideal population of a district), and summary fields. A redistricting plan is displayed as a color theme map with summary information in a table. As blocks or VTDs are added to a district, both the thematic map display and data table are updated. The base features (e.g. blocks) are merged into a new district layer from which the user can compute measures of compactness and check for completeness and contiguity.

Maptitude for Redistricting easily accesses database and spreadsheet files. It also imports the following formats of geographic and non-geographic files:

Geographic: TIGER/Line File; ARC/Info Ungenerate and Export (E00) files; Arch View Shape files; MapInfo Interchange format (MIF); and, Strategic Mapping (BNA) files and a few others.

Non-geographic: Numeric (DBF, Excel, and Lotus); Graphic files (BMP and Tiff).

Maptitude has a layout window where you can place one or more maps on a single document combined with data tables, charts and diagrams for printing. This feature is a plus for this program since it helps to move and resize objects for the purpose of presentation.

Maptitude offers a host of general GIS functions, including: data manipulation; map creation and modification; spatial queries; and advanced data operations such as producing reports, adding new fields or data, and importing or exporting various data formats. The software also features an array of redistricting features, including: geographic aggregation; calculation of ideal population; creation of district tables; testing for compactness, contiguity, and unassigned geographic elements; capacity to save plans in various formats; and, automatic computation of data values.

Maptitude for Redistricting includes a redistricting data CD, one year of maintenance (software upgrades and data updates), and ninety days of technical support. Call Caliper at 617-527-4700 for more information and prices.

Mekonnen Gessesse is a senior program officer in the Fair Representation Programs at the Southern Regional Council.