Maps are
essential in the redistricting process, but obtaining adequate maps can be one
of the most challenging obstacles facing officials in charge of redistricting.
While standard maps, such as road maps, identify geographic features and the
boundaries of administrative areas such as counties, cities and towns, they may
not necessarily provide sufficient detail for drawing electoral districts.
If redistricting is based on a census count of the population, then the maps must show the boundaries of the census geographic units for which population statistics are available. If redistricting is based on the number of registered voters, then the maps must show the boundaries of the voting areas for which voter registration statistics are available. The boundaries of the existing electoral districts are usually needed as well.
Considerable time and effort may be needed to assemble the necessary maps and to determine the precise boundaries of the new district lines on these maps. Sufficient detail is needed to enable election administrators to assign each and every voter to an electoral district. This can be a very difficult and time-consuming process, even for jurisdictions with technologically sophisticated computer mapping systems.
In the United States, maps provided by the Census Bureau were once drawn by hand and, as a result, were often difficult to read and frequently filled with errors. In preparation for the 1990 census, however, the Census Bureau created a computerised database of the entire country called TIGER (Topographically Integrated Geographic Encoding and Referencing). The TIGER database depicts:
- visible geographic features such as roads, rivers, and railroads;
- a whole hierarchy of census geographic units (for example, census blocks, block groups, and census tracts) for the collection and reporting of population data;
- the boundaries of administrative subdivisions such as counties, cities and towns; and
- political geography such as congressional districts and, in some cases, voting areas, referred to as election precincts in the United States
Maps produced from the TIGER database for use with GIS (geographic information systems) software provide redistricters in the United States with uniform, digitised maps on a county-by-county basis for the entire country. The availability of these maps has made the process of district building in the United States more accurate and less time consuming.
Very few countries, however, have computerised maps available for redistricting purposes – most redistricters have access only to paper maps. Depending on the country, there can be serious problems with accuracy, legibility and differing scales with these paper maps. Digitised computer maps of the country can be created, but only at an enormous cost. Of course, these detailed computer maps can be used for many purposes other than redistricting and, therefore, may be worth the time, effort and expense.
