Geoscience Reference
In-Depth Information
Remotely sensed image
Geological faults
Transportation network
Population density
Topography and
vegetation
Figure 2.32 GIS layers. Each layer represents a distinctive part
of the landscape, such as topography, vegetation, population
density, or the local road network. When these layers are inte-
grated, they form a detailed image of the landscape.
Systems, or GIS. A GIS is a system for storing, analyzing,
and manipulating spatially referenced data, usually in
digital form in a computer. Most GIS databases consist of
a series of individual data layers that are considered to be
relevant for the study being conducted. A data layer contains
measurements obtained with respect to a specific geographic
variable, such as vegetation, soils, road networks, municipal
boundaries, and the distribution of surface water (hydrology)
in lakes and rivers.
Let's choose vegetation as an example. A geographer may
desire to map the spatial distribution of trees and grassland in
a region, which can be determined by using infrared remote
sensing or by digitally tracing old maps. In so doing, a GIS
layer is created that can be identified as “vegetation” in the
overall database. A variety of attributes can be subsequently
assigned to this layer, such as species composition, height,
slope of the land, and condition. Subsequently, similar maps
can be created for other desired variables, resulting in layers
for each of them. Now look at Figure 2.32, which shows a
potential series of GIS layers from a theoretical study area.
Notice how these layers exist as distinct units that can stand
alone. In addition, the layers can be combined to illustrate the
overall geographic character of the region. It is beyond the
Figure 2.31 Using GPS to measure landscape change. Given
the high accuracy of some GPS systems, it is possible to monitor
changes in ground elevation, such as those that may occur near
the Augustine Volcano in Alaska due to renewed volcanic activity.
multipath error , which results when obstructions such as build-
ings and trees cause the incoming GPS signal to be deflected be-
fore it reaches the receiver. This deflection confuses the receiver
because two slightly different signals arrive at the same time.
Geographic Information Systems
Another tool that is very important in the way that
geographers do their work is Geographic Information
Multipath error Error that results when a satellite signal
reaches the GPS receiver directly from the satellite as well as
others reflected from nearby buildings or other surfaces.
www.wiley.com/college/arbogast
Using a Geographic Information System
To get a feel for GIS, view the animation Using a Geographic In-
formation System . This animation focuses on the 2010 oil spill
in the Gulf of Mexico and illustrates the way that GIS could be
used to assess the character of the spill and its geographical
relationship to various aspects of the regional environment and
economy. After you complete the exercise, answer the questions
at the end to test your understanding of Geographic Information
Systems.
 
 
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