Geography Reference
In-Depth Information
ing events into patterns.
Monte Carlo simulations
offer the means to create
data that stochastically offers a reliable estimation of the geographic differ-
entiation of continuous characteristics—for example, soil pH, species densi-
ties, or transportation costs.
Fuzzy-set theory
is the foundation for a number of
geographic information analysis operations that consider the variability of
natural phenomena boundaries and the inaccuracies of data collection.
Var i-
ance
measures the difference between repeated measures of the same prop-
erties. It is important in assessing the impacts of different geographic aggre-
gation units on the accuracy of data.
GIS in a Nutshell
With many text books offering varying introductions to GIS, the purpose of
this section is only to show GIS's relationship to geographic information
analysis operations and the role of GIS in representation and communica-
tion. Consider two definitions followed by a third that brings aspects of
them together.
First Definition
A system of hardware, software, data, people, organizations and institutional
arrangements for collecting, storing, analyzing, and disseminating information
about areas of the earth
(Duecker & Kjerne, 1989).
This commonly cited definition focuses on important parts of a system
that consists of six components and is used for four generic purposes. It can
be used to describe any organized use of geographic information. GIS defi-
nitely involves these components and is used in these four ways. If we con-
sider the terms very broadly—for example, hardware includes notecards and
software includes alphabetical filing systems—then even an address list could
be considered to be a GIS. In this definition, GIS is used as a single system
for all elements of processing GI, beginning with collecting and ending with
making maps and other types of information.
What about the geographic representation and cartographic representa-
tion? Duecker's and Kjerne's definition provides insight into what GIS can
be used for. What about how, by whom, and for whom? If you know what
the GIS is being used for, then this definition is practical because it lends
great flexibility for actually using a GIS in many different ways. It also may be
too vague in how it explains the relationships between the components and
generic purposes. Are all components equally involved in storage? This
seems to be a naïve question, but with this definition standing on its own, as
a definition should, you really couldn't tell. This definition is handy, but
what most people understand when they rely on this definition is just the
surface of GIS; the geographic representation and cartographic representa-
tion are missing.
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