PRESENTING YOUR RESULTS - A Guide to Conducting Online Research - page 142

relation to environmental factors in the vicinity; the migration of ancient or
modern populations across a region; voter preferences by county; and ethnic
population distributions. Some studies involving mapping can be found in Lai
and Mak (2007), Sinton and Lund (2007) and Knowles (2008).
The tools for displaying maps and associated data range from the very com-
plete Geographic Information System (GIS) applications like ArcGIS from
ESRI (http://esri.com/products.html), to open-source GIS applications like
GRASS (http://grass.itc.it) and OpenMap (http://openmap.bbn.com), to other
more general purpose applications that also draw maps such as Canvas ,
Matlab or IDL , and finally to web-based applications like GoogleMaps .
The term Geographic Information System arises because these applications
allow the investigator to associate points on a map with other data. The pro-
fessional packages like ArcGIS and the GIS component of SAS include a large
collection of maps and locations, database management tools, and methods to
analyze and display the information. Outside of these tools, there is a huge vari-
ety of map data available on the web. The book Mapping Hacks (Schuyler et al.,
2005) is a useful starting point for the discovery of such data, and also of many
interesting things that can be accomplished with geographic data. Their focus
is mostly on open source software tools.
GIS programs like ArcGIS and others distinguish between three types of data:
raster, vector and attribute. Raster data are a grid of values, for instance surface
elevation or a scanned photograph, and are usually used as a background for the
map. Vector data are also called shape data (particularly in ArcGIS), and
includes points, lines and polygons. These are usually used to represent, for
example, national boundaries, rivers, streets, buildings and city locations.
Attributes are text and numbers that can be associated with a shape or vector
item. Attributes are stored in a database format, and can be manipulated with
database commands. A powerful feature of GIS systems is that as vector ele-
ments are combined or divided, the associated attributes are aggregated along
with the vector elements, allowing for very sophisticated analysis of spatially
organized data.
Another paradigm in many GIS programs is the use of layers, as similarly
used in graphics tools like AdobePhotoshop and GIMP . All raster elements
and vector elements are associated with a layer. The user can at any time select
which layers to include in the analysis or display of the map. This way several
different appearances can be generated from the same data.
ArcGIS
The ArcGIS tool comprises four products: ArcReader , ArcView , ArcEditor and
ArcInfo . ArcReader is available as a free download from the ESRI web site and
enablestheviewingandprintingofexistingmapscreatedwiththemoreadvanced
tools. ArcView can be used to prepare maps and make queries about attribute
data. ArcEditor includes additional data creation and editing tools, and ArcInfo