Location, Trigonometry, and Measurement of the Sphere - Spatial Mathematics: Theory and Practice through Mapping - page 43

devised, or because the city founders wanted all or most of the addressing for
the central part of the city to be on one side of one of the axes, or because of
a natural feature such as a river, or for other reasons. In many cities, addresses
are referenced from these two axes, typically with a range of 100 between
each block. Often, even and odd were given designated sides; for example, in
Denver, Colorado, addresses on the east and south sides of streets are even,
while addresses on the north and west sides of streets are odd. Thus, a house
on Broadway that is three blocks north of the X -axis on the east side of the
street could have an address of 308 North Broadway.
It is worth noting that unlike latitude and longitude, the addressing system
sometimes is not rigorously followed in a city that has officially adopted it,
and may be totally ignored in other cities. Indeed, in some places, addresses
do not follow a regular system, and in others, such as Tokyo, houses are given
successive numbers depending on when they were built on the block. Hence,
the system there is historical rather than geographical. In scores of other cit-
ies and rural areas around the world, there are no street addresses at all, and
in many cities, very few of the streets even have names. In the United States,
until relatively recently, most rural addresses used the “route and box” sys-
tem. The route represented the route of the postal carrier, and the box was
a physical mailbox along that route; for example, Route 4, Box 358, Mequon,
Wisconsin. While the boxes and the routes may have been numbered con-
secutively, there was much ambiguity and duplication; it was physically dif-
ficult to locate a house or apartment with this system. When there is an
addressing system in place, it can serve as an absolute and unique identifier
of residences, industrial sites, and businesses in that location. Addressing is
so valued as a way of locating homes in the event of an emergency that many
rural addressing programs over the past 20 years in the United States have
been undertaken. These addressing programs are aimed at converting the
“route and box” addresses to “house number, street” addresses.
A second coordinate system is the State Plane Coordinate System. Used exclu-
sively in the USA, this system consists of a set of 124 separate coordinate
systems, or “zones,” and each state is covered by one or more of them. The
boundaries of the zones usually follow county lines. A Cartesian coordi-
nate system is created for each zone by establishing an origin some distance
(usually 2,000,000 feet) to the west of the zone's central meridian and some
distance to the south of the zone's southernmost point. This ensures that
all coordinates within the zone will have positive values. The X -axis run-
ning through this origin runs east-west, and the Y -axis runs north-south.
X distances are typically called eastings (because they measure distances
east of the origin) and Y distances are typically called northings (because
they measure distances north of the origin). Some zones use feet, and oth-
ers use meters. The system is employed widely for spatial data used by and
distributed by state government agencies, in part because it uses a simple
Cartesian coordinate system to specify locations and in part because it is