Geoscience Reference
In-Depth Information
Visual ConCept CheCk
2.3
A variety of geographic information can be ac-
quired, stored, and analyzed using digital tech-
nology. This image is an infrared satellite image
of a portion of Washington, D.C. What do the red,
black, and bluish-gray areas represent in this
image? What are at least four data layers that
could be constructed in a GIS?
scope of this topic to describe GIS in detail, but you should
understand that it is an extremely powerful tool that is used in
a wide variety of ways, including:
such as road networks, location of sewer and utility lines,
and emergency traffic routes.
•
Business needs
—A growing number of companies are
incorporating GIS into their operations. GIS can be used,
for example, to preselect the most efficient delivery routes
that will save fuel costs. In addition, GIS can be used to
identify the best location for new shopping centers based
on surrounding demographic characteristics.
•
Environmental management
—GIS can be used to manage
spatial information associated with soils, wetlands, vegetation
species, topography, and the location of data collection sites.
•
Municipal planning
—GIS is used in virtually all cities,
large towns, and counties to manage spatial information
S U M M A R y O F K E y C O N C E P T S
1.
Lines of latitude are called parallels and determine lo-
cation north and south relative to the Equator. Latitude
designations are calculated using simple geometric prin-
ciples and extend to points 90° N and S, which are the
North and South Poles, respectively. Lines of longitude,
in contrast, are called meridians and determine loca-
tion east and west of the Prime Meridian in Greenwich,
England. These designations are also calculated using
the geometry of a circle and extend to 180° E and W.
Latitude and longitude overlay to form a geographic grid.
The United States uses another grid system, the United
States Public Land Survey (USPLS), to survey property
ownership.
example, maintains the correct shape of features at the
expense of their relative size.
3.
Map scale refers to the ratio of the size of features on a
map relative to the real world. Small-scale maps show
relatively large areas but with less detail. A large-scale
map, in contrast, shows a relatively small area but with
greater detail.
4.
“Remote sensing” refers to the ability to observe and
monitor aspects of Earth from a distance. The most sys-
tematic way to accomplish this task is with satellite plat-
forms such as the Landsat system. These systems mea-
sure emitted energy that can be stored as digital data
and ultimately accessed and manipulated by scientific
users.
2.
Maps are two-dimensional representations of three-
dimensional aspects of Earth. They are created through
the process of map projection, which creates distortion
in some aspect of the map. A conformal projection, for
5.
A Geographic Information System (GIS) is a digital data-
base that contains relevant geographic information such
