Spatial Analysis and GIS: A Primer

Understanding the spatial distribution of data from phenomena that occur
in space constitute today a great challenge to the elucidation of central questions
in many areas of knowledge, be it in health, in environment, in geology, in
agronomy, among many others. Such studies are becoming more and more
common, due to the availability of low cost Geographic Information System (GIS)
with user-friendly interfaces. These systems allow the spatial visualization of
variables such as individual populations, quality of life indexes or company sales
in a region using maps. To achieve that it is enough to have a database and a
geographic base (like a map of the municipalities), and the GIS is capable of
presenting a colored map that allows the visualization of the spatial pattern of the
phenomenon.
Besides the visual perception of the spatial distribution of the
phenomenon, it is very useful to translate the existing patterns into objective and
measurable considerations, like in the following cases:

· Epidemiologists collect data about the occurrence of diseases. Does the
distribution of cases of a disease form a pattern in space? Is there any
association with any source of pollution? Is there any evidence of
contagion? Did it vary with time?

· We want to investigate if there is any spatial concentration in the
distribution of theft. Are thefts that occur in certain areas correlated to
socio-economic characteristics of these areas?

· Geologists desire to estimate, from some samples, the extension of a
mineral deposit in a region. Can those samples be used to estimate the
mineral distribution in that region?

· We want to analyze a region for agricultural zoning purposes. How to
choose the independent variables – soil, vegetation or geomorphology –
and determine what the contribution of each one of them is to define
where each type of crop is more adequate?

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