1. From Teaching Geography, Second Edition, by Phil Gersmehl. Copyright 2008 by The Guilford Press.
Permission to photocopy is granted to purchasers of this book for personal use only (see copyright
page for details).
182

2. Teacher ’s Guide for Transparencies 1A and 1B
Transparency 1A is a bad example (and 1B is a good example) of a choropleth (CORE-oh-pleth)
map.
The choropleth map “language” is used to show information that is collected and reported
for political units, such as countries, states, counties, or election districts. Examples of such
information include census data, crime rates, and percentages of people who voted for a partic-
ular candidate.
Reporting information by political areas does not tell us about the internal arrangement of
things in an area. To avoid confusion, therefore, cartographers have adopted three conventions
about how to make choropleth maps:
1. Use choropleth maps only for ratio data (numbers you get when you divide two counts,
such as the amount of production and number of people, in order to get a ratio such as
production per person). That is what Transparency 1B does right. Map 1A uses
choropleth symbols to show counts. This can be misleading, because two small states
might actually have greater total production than a large state, but their lighter color
implies otherwise. It would better to use scaled symbols (e.g., circles of different sizes) to
show counts, because readers can visually compare the size of a graduated symbol with the
size of a state to get a more accurate picture.
2. Choose category boundaries carefully. Map 1A has numbers to show actual production in
the top three states. How different would the map seem if the darkest category had only
states with more than 10 billion dollars of farm products? This question raises an impor-
tant point: a map maker has plenty of chances to make choices that are not technically
“wrong” but still alter the impression that a map conveys. That realization is a useful
learner outcome.
3. Arrange colors in a logical sequence. The conventional rule is to represent low values with
light colors and higher values with progressively darker colors.
Activity: Have students find choropleth maps in magazines and newspapers. Did the authors of
the maps follow these three basic rules? You may be surprised how often they don’t. If you find
a particularly good (bad!) example, cover the legend and ask students which areas have the
highest values. Discussion should lead to two conclusions:
A map with poor category choices and/or a nonintuitive color sequence may accurately
portray each individual area, BUT
The reader has to work harder to see the overall pattern.
Since the clear depiction of spatial patterns is a major goal in making maps, students should
wonder whether someone who chooses awkward categories or a bad color sequence is just
ignorant or is deliberately trying to mislead.
Activity: Give students a table of numbers for an area with about 20 sub-areas, and have them
make choropleth maps with different numbers of categories and boundaries between them.
For a how-to manual with interesting data, get Thematic Maps: Visualizing Patterns, by Carol
Gersmehl, prepared for the Tennessee Geographic Alliance summer institutes and used in
many other states. I freely admit that I “borrowed” many ideas from this teacher-tested manual.
I also realize that the one-page discussion here is sketchy, but remember, this page has just two
of 85 example transparencies; keep reading!
183

3. From Teaching Geography, Second Edition, by Phil Gersmehl. Copyright 2008 by The Guilford Press.
Permission to photocopy is granted to purchasers of this book for personal use only (see copyright
page for details).
184

4. Teacher ’s Guide for Transparency 1C
This map is a greatly simplified 1:24,000 topographic map. Topographic maps like this are
available for most parts of the United States; go to www.topozone.com or write to the Map Distri-
bution Center, U.S. Geological Survey, Federal Center, Denver, CO 80225, for a (free!) index
map of your state, which you can use to select maps for purchase.
Activity: Put a topographic map of your local area on a bulletin board. This kind of map can
show familiar details in a new light, which can prompt lively discussion of subjects being cov-
ered in class and questions that students generate on their own.
A key to successful use of topographic maps is to know the advantages and limitations of
each scale. For example, a map with a scale of 1:24,000 (the fraction means that an inch on the
map is 24,000 inches or 2,000 feet in the real world) has a wealth of fine detail but cannot show
more than a few dozen square miles at a time. If you have a lot of display space, tile several of
these maps together to show a larger area. A subject the size of Atlanta, Georgia, and its sub-
urbs, for instance, would make an impressive wall display. A map of Georgia at that scale, how-
ever, would need a gymnasium floor.
The answer to this dilemma is to find other maps at different scales. The U.S. Geological
Survey also makes available maps at scales of 1:100,000; 1:250,000; and whole-state maps at
appropriate (smaller!) scales.
Teacher ’s Guide for Transparency 1D
At a scale of 1:250,000, a topographic map is useful for planning how to get from one place to
another. Maps at this scale show major roads, rivers, terrain features, and forest regions. As you
can see on this transparency, however, a 1:250,000 map cannot show individual buildings or
details such as the rapids in the river. In other words, someone looking at a map of Harpers
Ferry at a scale of 1:250,000 will miss precisely what seemed most strategically important at a
scale of 1:24,000, namely the presence of shallow water that makes the river easy to cross (see
the CD unit on Transitions).
This raises very important point: much of what we “know” about the world depends on the
scale at which we view it. It is therefore wise to examine places at several scales.
Activity: Have students gather as many different maps as they can find for a specific area. Look
at maps in newspapers, county and city offices, Chambers of Commerce, travel brochures (e.g.,
in rest stops and plazas on Interstate Highways), and road maps.
Then, post the maps (or copies of them) in scale order, with the most detailed maps at one
end and maps that cover an entire state or country on the other. Ask students to examine the
maps and tabulate what kinds of information appear at each scale. The flip side of that coin is a
good test question: “What scale map should you ask for if you want to find out about the pat-
tern of houses in Roseville? the distance from Moscow to Berlin? and so on?”
Extra: The DeLorme Company (www.delorme.com) has compiled books of topographic maps for
each state. Those books are great resources for class use, field trips, or personal travel!
185

5. From Teaching Geography, Second Edition, by Phil Gersmehl. Copyright 2008 by The Guilford Press.
Permission to photocopy is granted to purchasers of this book for personal use only (see copyright
page for details).
186

6. Teacher ’s Guide for Transparency 1E
Iron and steel mills were big business, particularly in the late 1800s. Like textiles in the early
1800s, autos in the mid-1900s, and computers in the late 1900s, these factories employed mil-
lions of workers. Moreover, they required the purchase of many other kinds of products, and
they provided “raw” materials for many other goods and services. As a result, during its peak
each of these industries had a great inf luence on patterns of wealth and population.
If you want to understand the world economy of the late 1800s, therefore, you have to look
at where iron and steel were made.
This map shows part of Europe. It is deliberately drawn with very faint lines for national
borders, because in fact these borders changed several times. Moreover, many of the interna-
tional tensions that led to wars in the 20th century involved control of key transportation
routes and the raw materials for iron and steel mills.
Activity: Show the transparency and ask which lettered places would be good locations for steel
mills. The names are not important for this activity, but in order from A to I, the places are a
mountain village in Norway; Birmingham, England; Paris, France; Essen-Dusseldorf in the Ruhr
Valley of Germany; Verona, Italy; the western end of the Carpathian Mountains; the port city
of Gdansk, Poland; Budapest, Hungary; Istanbul; Aleppo, Syria; the Donetsk area of Ukraine;
Banghazi, Libya; and Madrid, Spain.
Of those, D was and is the largest steel center; it is located close to major coal deposits and
is directly downstream from the largest iron ore mines in Europe. Places B and K are also
important. To make this Activity more analytical, read on.
Teacher ’s Guide for Transparency 1F
The recipe for steel is simple: mix coal, iron ore, and limestone. Cook well, making sure you
don’t burn yourself! Then cool the steel and ship it to the customers. Unfortunately, the raw
materials and buyers are usually in different places. As a result, people building a steel mill
must pick a compromise location (see the CD unit on Changing Technology).
This transparency graphically shows that a blast furnace needs more coal than ore, and
therefore it usually makes sense to put it close to coal mines. Moreover, since it is cheaper to
transport heavy material in boats than by other means, it usually makes sense to put mills on
major rivers or in ports. (Think of the locations of famous steel mill areas in the United States:
Pittsburgh, Cleveland, Detroit, Gary, Chicago, and Baltimore are all on navigable water, and
they all are much closer to sources of coal than to major deposits of iron ore, which are in
northern Michigan, Minnesota, and Brazil.)
Activity: Use this diagram to aid a discussion of Transparency 1E. Then, if desired, have stu-
dents try to draw a similar diagram showing the inputs and outputs of another industry.
Caution: Steel production is a “heavy” industry; the raw materials and final product weigh a
great deal and are expensive to transport. As a result, people try to locate factories between
the sources of raw materials and the market. Some industries have raw materials and prod-
ucts that are light and easy to transport. Those factories can be located almost anywhere.
Activity: Have students try to classify specified industries as heavy or light; for example, oil
refining (H), computer assembly (L), copper smelting (H), diamond cutting (L), grain milling
(H), and sewing shirts or backpacks (sort of in between). Heavy industries are usually located
close to raw materials. Most industries in the light and in-between categories tend to be located
closer to other inputs, such as skilled labor, capital, clean water, and so on.
187

7. From Teaching Geography, Second Edition, by Phil Gersmehl. Copyright 2008 by The Guilford Press.
Permission to photocopy is granted to purchasers of this book for personal use only (see copyright
page for details).
188

8. Teacher ’s Guide for Transparency 1G
A key to finding a good location for production in a heavy industry is to minimize the cost of
transporting raw materials. Assigning “penalties” to potential sites is a way to make analysis of
this factor more rigorous than simply “eyeballing” a map.
Activity: Use the map in Transparency 1E, but with the following calculations:
1. Estimate the distance from a source of coal or iron ore to your factory site.
2. Note whether the route goes over land or by boat.
3. Calculate the transportation penalty.
If this seems too easy for your students, you can add complexity in several ways. Add penalties
for crossing mountains or national borders. Add penalties for areas with severe air and water
pollution, such as the Ruhr or middle Elbe. Have them do research on mining and add penal-
ties for using low quality coal or iron ore.
Teacher ’s Guide for Transparency 1H
With Transparency 1F, this diagram helps introduce some really knotty policy questions:
What should people do when changing technology has made their town a less desirable
location for a particular kind of industry? (See the CD unit on Changing Technology).
What should people do when doing “what they always have done” is no longer competitive
in the international economy?
Phrasing a question in a particular way tends to restrict the range of options that might be con-
sidered. This is important for students to learn, because the two questions above really address
different aspects of the same issue. Emphasize that a decreasing ability to compete may not be
anyone’s “fault.” The human tendency is to seek a scapegoat – to blame factory owners, labor
unions, recent immigrants, or government policy for something that may be nothing more
(and nothing less!) than a geographic consequence of a change in technology.
It may be useful to put the question into a larger perspective: a change in technology has
made steel production more efficient and steel less expensive. Consumers in all parts of a coun-
try have gained, but producers in a few areas have been hurt. A humane society should take this
geographic fact into account in designing welfare and migration policies.
Activity: Assign roles (e.g., mayor, labor leader, minister, storekeeper, etc.) for students to play
in simulating a town that loses its major employer.
Transparencies 1E–1H can help a teacher show why an old steel mill may not be able to
compete with new electric furnaces in a location well suited to that technology. Or, if desired,
modify the simulation above to fit some other economic activity, such as a textile mill, a meat-
packing plant, a drive-in theater, or a small video store threatened by a new superstore. Have
students discuss the threatened business’s options: moving away, retraining for other work, and
so on. Have them prepare maps to illustrate the options. The key question is: Can the proposed
new activity work in the current environment? This is the big question of economic geography;
it can take years to learn how to answer it well. Four transparencies aren’t enough, but we have
learned enough to say that a society is in trouble if its citizens graduate from school and still see
no need to think about the locational consequences of technological change!
189

9. From Teaching Geography, Second Edition, by Phil Gersmehl. Copyright 2008 by The Guilford Press.
Permission to photocopy is granted to purchasers of this book for personal use only (see copyright
page for details).
190

10. Teacher ’s Guide for Transparency 1I
The basic idea of “per” data is simple: a quantity is divided by the number of individuals who
“share” it.
It must be admitted, however, that the real-world use of per data can be confusing, espe-
cially if we are not sure what is being divided by what. This raises a difficult question: how can
students accurately understand a newspaper or television story if they cannot figure out how
the tables or maps of per data were made? It helps, then, for teachers to use per data fre-
quently, so that students gradually improve their ability to interpret the results.
Activity: Project this Transparency and have students fill in the blanks by dividing the total land
area number by the population number. Since both numbers are expressed in millions, the mil-
lions “cancel out” and the result is the number of acres per person. Work through some of the
examples that have already been calculated – the answers for the blanks are 4.5 for Mexico, 1.0
for Germany, and 0.7 for Japan.
Once students get the idea, you can extend the discussion. For example, is the number of
acres per person the most useful per number, or would something else be more meaningful? It
might be noted that people cannot grow food in deserts or high mountains. Before doing the
calculation, therefore, it might be useful to know the proportion of the land that could be used
to grow food. To make a link to Transparency 1J, write the following numbers next to the coun-
try names: 13, 63, 5, 19, 14, 35, 13. These numbers indicate the percentage of land area that
can be used for crops (right, that’s another per number!). Multiplying Argentina’s 684 million
acres of land by 13 percent (13/100) gives a result of 89 million acres of cropland. The answers
to this calculation are in the first column of Transparency 1J.
Teacher ’s Guide for Transparency 1J
Repeat the recipe for “per” data: “take the quantity you want to measure and divide it by a num-
ber that can make the data meaningful.” Agricultural land, for example, is meaningful in terms
of how many people must be fed. A relevant per measure, therefore, is the number of acres per
person (the number of acres of cropland divided by the number of people).
Activity: Project this Transparency and have students calculate the number of cropland acres
per person (0.64 for Mexico, 0.37 for Germany, less than 0.1 for Japan; underscore that the
amount of cropland per person in Japan is less than 1/20th as much as in the United States).
These numbers, as Postscript 1-1 says, are one reason Americans are not as concerned as
people in other countries about “values” issues in geography. Compared with those of other
industrial countries, residents of the United States have always had plenty of cropland for food
and plenty of “empty” land for new buildings, roads, parks, waste disposal, and other uses. As
population increases, however, land issues become more important, which is one reason for
the present upsurge of interest in geography in America.
It is important to keep in mind that all land is not equally productive. This observation
leads to another kind of “per”data: yield per acre. The average yield of wheat per acre of cold
Canadian soil is much less than the corn yield in Iowa, and both are low compared with yields
in tropical Bangladesh or southern China, where farmers can get several crops of rice each
year. Almanacs or encyclopedias (or www.cia.gov) can provide data for calculating ratios such as
food production per person.
191