Geography Reference
In-Depth Information
CHAPTER
5
OVERVIEW
IN WHICH you explore some ideas
about collecting and selecting
data, including using the Global
Positioning System. Also you digitize
and edit map data, transform spatial
data, and examine combining
attribute data with geographic data.
Geographic and
Attribute Data: Selection,
Input, and Editing
In the Step-by-Step section of this chapter, you will gain
experience working with mostly small datasets. You will
examine the “nitty-gritty” of digitizing and manipulating
data. However, most GIS projects deal with large amounts of
data. Sometimes these datasets are found. Sometimes data are
collected from the field. What follows here is advice for getting
the right data for the products that might be produced by a
medium to large GIS project.
“Garbage in, garbage out.”
An often quoted, but seldom heeded,
admonition in the computing world.
Concerns about Finding
and Collecting Data
Datasets form the basis of GIS. These systems are sometimes
referred to as being “data driven” to emphasize the importance
adequate data plays in their operation. The products of a GIS
are the most important contributors to its utility; the data
are the chief ingredients of that product. The single message
emphasized by this section is that any determination of what
data are needed, and what the characteristics of those data
should be, comes after a very careful look at what sorts of
information products are required for specific decision making.
The products, one would hope, are developed to satisfy the
needs discussed in Chapter 2 and the requirements for analysis
that we will take up in later chapters.
Determining what datasets are needed is not an easy process.
It requires the concentrated effort of experts, from the decision
makers who will use the ultimately produced information
to the scientists who gather and analyze the data. The ideal
order of matching data to needs is from the specification of
the information product back to the data gathering—that is,
in the direction opposite from the one in which the process of
producing the information takes place.
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