Download Chapter 2

Chapter 2
Representations of Earth
Chapter Objectives
This chapter should enable your students to…






Understand how Earth and its regions, places, and locations are represented by
a variety of visual media.
Understand nature and importance of maps and map-like presentations of the
planet, or parts of Earth.
Understand the techniques and media that support geographic investigations
through mapping, location finding, spatial analysis, satellite and aerial
photographic imaging, and computer analysis of geographic data.
Realize the advantages and limitations of different kinds of representations of
Earth and its areas.
Understand how the proper techniques, images, and maps can be used to best
advantage in solving geographic problems.
Recognize the benefits of Geographic Information Systems (GIS), Remote
Sensing, and digital cartography.
Chapter Outline
I. Chapter Preview
II. Locations on Earth
A. Maps and Mapmaking
B. Location on Earth
C. Size and Shape of Earth
D. Globes and Great Circles
III. Latitude and Longitude
A. Measuring Latitude
B. Measuring Longitude
C. The Environmental Science Perspective
1. A Life-Support System
2. The Human–Environment Equation
IV. The Geographic Grid
A. Parallels and Meridians
8
B. Longitude and Time
C. The Environmental Science Perspective
D. The International Date Line
E. The U.S. Public Lands Survey System
F. The Global Positioning System
V. Maps and Map Projections
A. Advantages of Maps
B. Limitations of Maps
C. Properties of Map Projections
1. Shape
2. Area
3. Distance
4. Direction
D. Examples of Map Projections
1. The Mercator Projection
2. Gnomonic Projections
3. Conic Projections
4. Compromise Projections
E. Map Basics
1. Title
2. Legend
3. Scale
4. Direction
VI. Displaying Spatial Data and Information on Maps
A. Discrete and Continuous Data
B. Topographic Maps
VII. Modern Mapping Technology
A. Digital Mapmaking
B. Geographic Information Systems
1. What a GIS Does
2. Data and Attribute Entry
9
3. Registration and Display
4. Visualization Models
5. GIS in the Workplace
VIII. Remote Sensing of the Environment
A. Aerial Photography and Image Interpretation
B. Specialized Remote Sensing Techniques
C. Multispectral Remote Sensing Applications
Lecture Suggestions

Being able to communicate the location of a place to others is a basic human
need, important to people today as well as to the earliest humans.

Maps are graphic models that depict a certain area or region, and their main
purpose is spatial communication—that is, to convey spatial information and
locations about the place that it shows.

Showing (and explaining) visual examples of map distortion, map types, aerial
photographs, and remotely sensed images is the best way to illustrate these
tools and their applications as used by geographers and other scientists.

Many people work in careers dealing with physical geography, applying their
educational background with the skills, tools, and technologies used in dealing
with environmental concerns.
Key Terms and Concepts
navigation
cartography
oblate spheroid
great circle
hemisphere
small circle
coordinate system
North Pole
South Pole
equator
latitude
sextant
prime meridian
longitude
geographic grid
parallel
meridian
time zone
solar noon
International Date Line
U.S. Public Lands Survey System
principal meridian
base line
township
10
section
global positioning system (GPS)
map projection
conformal map
Mercator projection
equal-area map
equidistance
azimuthal map
rhumb line
gnomonic projection
compromise projection
legend
scale
verbal scale
representative fraction (RF scale)
graphic (bar) scale
magnetic declination
azimuth
bearing
thematic map
discrete data
continuous data
isoline
topographic contour line
contour interval
profile
gradient
digital elevation model (DEM)
vertical exaggeration
geographic information system (GIS)
geocoding
visualization models
remote sensing
aerial photograph
digital image
pixel
resolution (spatial resolution)
near-infrared (NIR)
thermal infrared (TIR)
radar
imaging radar
side-looking airborne radar
weather radar
sonar
multispectral remote sensing
color composite image
Answers to Consider & Respond Questions
M.A. = Many answers possible
1. M.A. for vacation spot. It would depend on the purpose of your visit. If you were
going walking or sightseeing in town, an official city map would be best. If you were
hiking, a topographic map would best serve your purpose. Topographic maps show
actual elevations with numbers, satellite images show a photographic like vertical
image of the landscape, often in full color to see vegetation patterns. For example,
road maps show distances by automobile travel and the names of roads. All three
provide general impressions of the geography of the area in question, and all three
would show major roads. [Topographic maps: p. 63-62; Appendix B, p. 47-50;
Satellite images p. 54-55]. (Road map from student’s own familiarity).
2. M. A. The answer will vary greatly among students. Some important layers would be
roads, campsite locations, slope, geology, vegetation, location of natural resources,
soils, elevations, locations of wildlife sightings, water bodies, and other park
amenities. [p. 52]
11
Answers to Apply & Learn Questions
M.A. = Many answers possible
1. If it is Tuesday, 2 am in New York (75° W time zone—EST), it is 3 hours earlier in
California (120° W time zone—PST), which would be 11 pm on Monday night, (3
hours earlier for every 15 ° west and later for every 15° east). [pp. 34, 35, 36]
London is in the 0° time zone (GMT), and 75° east of New York, so it is 5 hours later
than New York (75/15 = 6), or 7 am in London on Tuesday. [pp. 34, 35, 36]
Sydney is in the 150 degree E time zone, east of London, so the time is 10 hours later
or 5 pm Tuesday in Sydney, Australia. [pp. 34, 35, 36]
2. If the linear scale is 1/2400, and vertical is 1 in = 100 ft. Convert to same units: 1 in =
1,200 inches, or an RF of 1/1200. 1/1200 is a fraction that is 2 times larger than
1/2400, so that is the vertical exaggeration—2 times the horizontal scale. [pp. 48, 49,
51]
3. Students should use the formula: map distance/Earth distance = 1/ Representative
Fraction Denominator. 10cm = 1km, change to meters: .10m = 1000m, so-.10m/1000m = 1/RDF or 1/10,000. In feet/inches: 3.94 in = 3281.12 ft—so change to
same units 3.94 in = 39,372 inches (12 inches x 3281.12). So--- 3.94/39,372 = 1/RFD,
and RFD = 9993 or an RF scale of 1/10,000 if rounded off. Important: the units in
an RF cancel out, so an RF scale is a dimensionless number. [pp. 43-45, Appendix B]
Answers to Interpreting the Map – Laguna Beach, California
1. 20 feet. [p. 62]
2. One inch on the map equals 24, 000 inches on the surface of Earth. [p. 43]
3. 912 feet on a hilltop above boat canyon. [p. 63]
4. About 600 feet below sea level off shore, and sea level (0 feet elevation) at the
coastline. [p. 63]
5. The west side is steeper, because the contour spacing is narrower. [p. 63]
6. The stream flows south. We know this because the "v" shapes of the contour lines
point upstream, and the stream flows in the opposite direction to the point of the "v."
[p. 63]
12
7. The northwest section of the coast is shown in the photo, from just NW of Crescent
Bay to NW of Abalone Point. [p. 63]
8. (Use Appendix B for a symbol legend) Cultural features: Churches (box with cross,
schools boxes with pennant flag), roads trails highways, street grid patterns, and
parks. New beachfront homes lining the coast northwest of Abalone Point. [p. 63]
Answers to Figure-Legend Questions
M.A. = Many answers possible
Figure 2.1
M.A. Knowing where to find food and water sources and how to
communicate that locational information was important to their survival.
[p. 30]
Figure 2.2
These hand-drawn depictions of the landscape are valuable, and very good
at emphasizing the topographic features and give a good impression of the
lay of the land. [p. 31]
Figure 2.3
Earth’s shape is very close to being a perfect sphere, so its deviations from
sphericity cannot be seen when viewing the planet from space. [p. 32]
Figure 2.5
Mansfield is at C-6. F-3 is the location of Cleveland. [p. 33]
Figure 2.6
90° N latitude. Note: the north and south poles do not require a longitudinal
position. [p. 33]
Figure 2.7
Sextants are mechanical devices that operate without relying on any power
source (other than that provided by the human operator). A batterypowered GPS unit could fail (imagine that if you were lost in a remote
area). Further, a sextant provides a good demonstration of relationships
between Earth and the Sun, and how those relationships are linked to
seasons and latitudinal position. In comparison, however, GPS provides
both longitude and latitude and can be used either day or night —or when
clouds obscure the sun. [p. 34]
Figure 2.8
Meridians converge, parallels do not; all meridians are half great circles, all
parallels are small circles except the equator; meridians are true northsouth running lines; parallels are true east-west running lines. [p. 34]
Figure 2.9
Answer will vary depending on the student’s location. [p. 35]
Figure 2.10 The International Date Line has been jogged around a few locations to
insure that countries, cities, towns, or island groups do not have different
13
days within their borders. [p. 36]
Figure 2.11 The Township and Range System was developed after the eastern United
States was settled. Thus, its impacts on land and distributions are seen
only in the Midwest and western portion of the United States. [p. 36]
Figure 2.12 SE l/4 of the SE 1/4, Sec. 20, T3S, R2E. [p. 37]
Figure 2.13 Mountain ranges of this magnitude do not exist in the Midwest. [p. 37]
Figure 2.15 The use of GPS technology is becoming commonplace. A GPS unit can
broadcast its position (e.g., placed in cars for location in theft recovery),
and they are useful for wilderness hikers to find their positions relative to
a map. Emergency vehicles have GPS units, so that a 911 operator can tell
where the nearest emergency vehicle is to a place of need, or how to find a
location—and thus allows faster response times. [p. 38]
Figure 2.17 The moon has been mapped using satellite observations of the terrain on all
sides of our lunar neighbor. [p. 39]
Figure 2.18 We use different map projections for many reasons; sometimes a certain
projection fits the shape and latitudinal area of the area we wish to present
on the map. Other times we may wish to preserve a particular map
property, such as shape, distance (area), or direction. [p. 40]
Figure 2.19 The distortion is very great in regions away from the Equator. Greenland
appears larger than South America on a Mercator projection when in fact
it is only about 1/8th the area of South America. [p. 41]
Figure 2.20 The answer depends on the intended use of the map, if it is important to
compare areas of regions, countries, continents, or other areas, preserving
area is best, if it is important to show the accurate shape of the same kinds
of areas, than preserving shape is more important. No map of a large area
can do both [p. 42]
Figure 2.22 The Mercator projection does not distort shape but the gnomonic projection
does. Both projections distort size. Most importantly a straight line on a
Mercator projection is a line of true compass heading, while on the
gnomonic projection a straight line represents the shortest route between
two points. [pp. 41, 43]
Figures 2.23 On these compromise maps, the continents are shown with reasonably good
shape preservation and reasonably good size proportion. In the interrupted
map (a) the distortion is shifted to the oceans —this map would not be
useful for sea navigation. [pp. 41, 44]
14
Figure 2.25 1:100, 000 is a smaller scale and a smaller number. The smaller scale map
(1:100, 000) shows more land area-but the features shown are smaller. [p.
45]
Figure 2.26 Navigating with (or using) a magnetic compass, it is important to know the
magnetic declination of our location, because the compass must be
adjusted for the local declination in order to get a reading corrected to true
north. Otherwise, we would not really know which direction we are
heading, without correcting the compass reading for declination. [p. 46]
Figure 2.27 Answer will vary depending on the student’s hometown. [p. 46]
Figure 2.28 M.A. Examples: discrete occurring only at specific locations —mountain
peaks (point), thunderstorm cells (area), coastline (line), and continuous
means any variable that has a measurable variable everywhere (air
pressure, vegetation cover density). [p. 47]
Figure 2.29 Students should be able to get a general impression of the landscape by
examining the topographic contour lines, particularly their shape and
spacing. [p. 50]
Figure 2.30 Looking at the spacing, shapes, and arrangement of contour line patterns we
can visualize the relief. Close spacing of contours means steep terrain and
wide spacing means a more gentle or perhaps nearly flat slope. [p. 50]
Figure 2.31 3800 meters on this elevation model is stretched in the vertical by three
times (less distance per length), so that same length horizontally would
equal 3800 times 3 or, 11,400 meters (3x more distance in the same length
than on the vertically exaggerated scale). [p. 51]
Figure 2.32 The high potential earthquake hazard for the East Coast and the Midwest
area near St. Louis, Missouri, and also earthquake hazard in New England.
[p. 51]
Figure 2.33 A Geographic Information System (GIS) has almost unlimited uses in
addition to environmental —any situation that requires spatial information
combined in layers can benefit from a GIS. This includes allocation of
emergency response systems, finding the best (or worst —places to
definitely avoid) locations for an economic, recreational, or agricultural
activity—virtually any kind of activity. [p. 52]
Figure 2.35 The scene may look natural, but it is exaggerated in the vertical, this
enhances the terrain and makes slopes look steeper than they really are. [p.
54]
Figure 2.36 Oblique views have a more natural scene to a normal human visual
15
perspective. Vertical views are more map-like. [p. 55]
Figure 2.37 Near-infrared (b). Near infrared images show a stronger contrast between
water (dark blue) and the red growing vegetation; so it is much easier to
see the boundary between land and water (important for making maps of
the location). Crops and other vegetation types can also be discriminated
better on the color infrared photograph, than on the normal color print. [p.
55]
Figure 2.38 It is important to know where storms are located and what areas they are
moving toward, as well as how fast they are moving. [p. 56]
Figure 2.40 Weather radar produces a display that is much like a map of precipitation
patterns—where rain, snow, or hail are falling and in what intensity.
Imaging radar makes an image of the land surface —slopes, hills, valleys,
plains, and mountains. [p. 50]
Figure 2.41 Examples: We can see road and street patterns, a bridge across the center of
the lake, and boundaries between land and water. Differences in water
color are indicators of changes in depth or sediment load. Patterns of fields
and other plots of land can be seen, including an urban area on the lake
shoreline in bottom of image (gray). The winding and muddy channel of
the Mississippi River is visible. [p. 59]
16