Database Reference
In-Depth Information
In the postal address, the county reference (Hampshire) has been replaced by
a post town (Southampton). However Warsash is not within the boundaries of
Southampton, but from a postal perspective, the post for Warsash is directed to the
main regional sorting office in Southampton. Postal addresses do not always differ
from geographical addresses, but one needs to be aware that postal geography can be
quite different from what one might term a natural topographical geography. Postal
addresses also frequently have a postcode or zip code, again intended to aid the
postal service in delivering the mail by enabling addresses to become more easily
machine readable. A number of geographically close addresses will all share one
postcode. These codes can be used to create their own geographies as they pro-
vide easily referenceable labels that can be used to associate information about that
postcode area. For example, someone could associate health statistics to postcodes,
enabling the health of an area to be mapped without identifying individual addresses
and thus protecting personal information. However, it needs to be remembered that
postcodes can change, and that they do not really identify areas, just a collection of
individual postal delivery points. The area associated with a postcode or zip code
can also vary enormously and will be much smaller in cities than rural areas.
3.4
REPRESENTATIONS AND USES OF GI
3.4.1 m
aps
A map, a two-dimensional representation of the landscape, is the most obvious man-
ner in which we think about GI being represented. The most common form of maps
is generalized maps that do not show an area precisely but allow clarity of informa-
tion visualization to take precedence over exact positional accuracy.
In generalized maps, things such as roads are often enlarged (broadened) to
emphasize them, unimportant buildings may be removed to reduce clutter, and
important buildings may be represented as symbols to highlight them. Another type
of map, less well known to the general public, is the planametric map; precision is
king, and all things are shown in their correct proportion and relationship to other
map objects. Such maps are typically used by builders and utility companies, for
land registration and other applications where the exact layout is required. Topologic
maps are also another popular representation. Such maps show the relative relation-
ships of the mapped objects but are imprecise in locational terms. The most famous
example of a topological map is the London Underground map. It has generated
many maps that have adopted its style, such as the Milky Way Transit Authority map
shown in
Figure 3.5
.
Maps are used for a number of distinct purposes, the most common being
•
Navigation
•
As a backdrop to overlay other information
•
As a way to visualize aspects of a landscape
Maps are therefore primarily for information visualization, at least in the tradi-
tional sense, and therefore are less relevant to Linked Data and the Semantic Web,
