Initiative Constitutional Amendment
How Automation Works
- This page includes a large animation of the process (below), which may
take a few minutes to load. The following discussion explains the main
- The Bureau of the Census maintains extensive mapping facilities and
conducts the 2000 census, accumulating fairly extensive demographic
data. The only element allowed by the Initiative is raw population
figures. These numbers are grouped by census tracts, with many broken
down into subsets called census blocks (BNAs). Apportionment does not
require this level of detail, so BNA counts are consolidated into
their parent tracts. Tracts naturally follow major geographic
boundaries and respect county borders within the individual states.
- The Bureau Mapping Service maintains a complete geographic record of
tract boundaries,which can be used to determine center points
(centroids) for each tract. Since the common reading and numbering
system is from left to right and top to bottom, the automation
sequence uses a northwest to southeast scan of the tract centroids to
start the automation process. This can be accomplished easily by
following the longtitude and latitude array diagonally.
- Once a starting point is established, a simple process of accumulating
tracts that are closest (most proximate) to the center of the district
can be accomplished with simple distance measurement to tract
centroids. As each tract is added, a new district centroid is
calculated and the population of the district is checked to see
whether it has come within the one percent (1%) population variation
allowed by the Initiative.
- The process starts by creating state Assembly districts (80), which are
then nested in pairs to create state Senate districts (40) and in
sequential sets of twenty for the state Board of Equalization
districts (4). Finally, US Congressional districts (52+) are created
with the same methodology as the Assembly districts.
- The following animation, from actual census maps, shows the process as
it begins in northern California.