Exploring Maps - Information - What else is here?
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Exploring Maps — Information
What else is here? purpose. Maps are the result of actual size on the ground. Scale can
conscious design decisions. be indicated three ways. The bar
Maps are made for many reasons, Cartographers decide how to scale is a line or bar that has tick
and as a result, maps are of many generalize and symbolize what they marks for units of distance. The bar
kinds. Some made for general are trying to show. They select scale is especially important because
purposes may show roads, towns and features (or themes) to show and it remains accurate when a map is
cities, rivers and lakes, parks, and omit other features. They often enlarged or reduced. A verbal scale
State and local boundaries. One generalize the data, simplifying the explains scale in words: “one inch
example of such a versatile map, or information so that the map is easier represents 2,000 feet.” The
base map, is the 1938 topographic to read. representative fraction is a ratio
map which portrays natural and such as 1:24,000, in which the
man-made features of an area. Other In choosing the scale, mapmakers numerator (l) represents units on the
maps are much more specific, determine how large an area they can map and the denominator (24,000)
conveying information primarily on map and how much detail they can represents units on the ground; in the
a single topic. A map that depicts show. The selection of symbols example of 1:24,000 scale, one unit
earthquake occurrences throughout (which can include lines, patterns, (any unit—feet, millimeters, miles,
the United States is a good example and colors) also affects the legibility, etc.) on the map represents 24,000 of
of a special-purpose map, or aesthetics, and utility of the map. the same units on the ground.
thematic map. Every map is made
for a purpose and serves that purpose Cartography blends science and art. Scale controls the amount of detail
best. A beautiful map may become and the extent of area that can be
popular, even though it may be less shown. Scales can be described in
The history of civilization has been accurate than a plainer version. relative terms as large scale,
illustrated by maps—battle maps by Details of cartographic style affect intermediate scale, and small scale.
soldiers, exploration maps by empire how a map is perceived, and A large scale map (for example, the
builders, thematic maps by scientists. perception varies with perspective. 1886 Sanborn map, originally at
By modern convention, and for no In short, people understand the world 1:600 scale) shows detail of a small
scientific reason, modern maps are differently, have different modes of area; a small scale map (for
usually oriented with north at the expressing this understanding in example, the 1877 geologic map of
top. But Al Idrisi’s 1154 world map maps, and gain different north-central Colorado, originally at
shows the Arabian Peninsula in the understanding from maps. 1:253,440 scale) shows less detail,
top center of the map, with south at but a larger area. (A comparison of
the top. Contrast this map with the Geographic features can be shown at representative fractions shows that
1452 Leardo world map. Different different sizes and levels of detail by 1/600 is larger than 1/253,440.)
societies in different places literally using scale. Maps include selected
have different perspectives, which basic geographic information to The humourous 1893 quotation from
may result from differences in provide context. Every map has a Lewis Carroll (on Poster Side 2)
physical geography, language, purpose or theme. The map design, illustrates this point by taking scale
religion, cultural values and which includes artistic aspects such to the extreme. Some small scale
traditions, and history. as composition and balance, affects maps are regional compilations of
the success of the map—that is, its more detailed maps, bringing
Even within a culture, a time, and a ability to communicate. information together for the first
geographic realm, maps can vary time at a common scale.
widely. This is because a map shows Scale is the relationship between the
the cartographer’s bias as well as the size of a feature on the map and its
U.S. Department of the Interior
U.S. Geological Survey —1—Exploring Maps — Information
Context is information that serves to of reality, will look for clues to the Generalization and grouping
orient the map reader to the mapped cartographer’s purposes and biases. dramatically affect the message the
place. As you look at the maps in the map presents by simplifying the data.
Poster Side 1, you may look for The information collected for a
familiar features (such as the “boot” mapping project is called spatial The success of a thematic map
of Italy) to identify the area shown. data. Any object or characteristic depends on map design. Scientific
Geographic information that that can be assigned a geographic maps like Edmund Halley’s 1701
provides context can include location can be considered spatial map of compass variations usually
coastlines, boundaries, roads, rivers data. Spatial data always include show only enough geographic data to
and lakes, cities and towns, location, but many also include orient the user, while emphasizing
topographic features, place names, values to be represented. the content. Halley, for whom the
and latitude and longitude. comet is named, pioneered several
These two kinds of information are cartographic techniques. The 1701
Distortion is another important qualitative data (for example, map introduced isolines, lines of
aspect of context; every flat map of a schools, roads, rivers, States) and equal value, a technique now used on
curved surface is distorted. The quantitative data (for example, topographic and other kinds of maps.
choice of map projection determines altitudes, amount of precipitation, The1886 Sanborn fire map includes
how, where, and how much a map is per capita income, population as much as it business purpose
distorted. It is important to density). Qualitative data, while not requires, but nothing more.
understand the kind and amount of numeric values, may be ranked, as in Triangulation maps, such as the 1744
distortion on the map sheet. The categories of roads or schools. map of France, show the network of
typical mapping project now plots points and lines, in this case
information on a base map, which Quantitative data can be treated in colorfully framed within national
shows where the place is and many ways. The cartographer may boundaries. The 1989 earthquake
establishes the scale, orientation, first decide to generalize data. map of the United States indicates
context, and spatial distortion of the Several closely spaced points may be the relative hazard by a contoured
information to be mapped. The type generalized to one symbol; features and colored surface, which also
and scale of the mapping project may be eliminated as map scale is shows State boundaries.
affect the choice of base map. reduced; questionable data may be
Digital, or computerized, mapping eliminated where other data are
frees the cartographer from some sufficient.
constraints imposed by a base map,
because features can be readily Likewise, grouping of data can be
selected or deleted, and the done in different ways. Large ranges
projection and scale can be changed of numbers may be grouped with
easily. breaks at round numbers (for
example, 10, 20, 30) or at statistical
A map’s purpose is usually clear mean and standard deviation values;
from its title and explanation, but in this case, the individual points
other information (author, date, may be mapped in various colors or
publisher, source of funding, etc.) sizes to correspond with group
hints at why and for whom the map values. Another way to group data is
was made. A knowledgeable map within geographic areas, using colors
reader, recognizing that a map is or symbols for areas, rather than
both a simplification and a distortion symbols at each data location.
U.S. Department of the Interior
U.S. Geological Survey —2—Exploring Maps — Information
Activity I: points to see the pattern in the
On the Trail of Knowledge data. Decide on symbols to use
in plotting the data. Consider
making a sample plot of some
Plot the earthquake epicenter data
data points to test symbol size,
(figs. 1-2), on the base map of the
color, etc.
North Atlantic ocean floor. Use
different symbols or colors to
3. Plot data points by latitude and
characterize different values.
longitude coordinates on the
base map. Use a ruler as needed
Time:
to help estimate locations
between latitude and longitude
One 50-minute class period.
lines. Choose a descriptive title,
and make a scale and legend for
Materials:
the map.
• Earthquake data (fig. 2)
4. Discuss the pattern revealed
• Base map (fig. 1) from mapping the data. Discuss
the fact that two tsunami
• Colored pens or pencils warning centers monitor the
Pacific Ocean, but none
• Ruler monitors the Atlantic. What does
this imply about magnitudes of
• Scrap paper earthquakes in the Pacific
Ocean? (Note that Magellan
commented on the
Procedures:
appropriateness of the name of
the Pacific Ocean.)
1. Study the data to learn what
information you have and to
determine the range of values. Extension:
This may be easiest to do by
Referring to the 1957 map of the
reorganizing the data in a new
ocean floor, and the quotation from
list or table. What are the lowest
Tharp’s book, discuss this example
and highest magnitude values?
of the process of scientific discovery.
Considering that the Richter
scale of earthquake magnitude
includes values from 0 to about
9, are mid-Atlantic earthquakes
weak, medium, or strong?
2. Consider generalizing or
grouping data to simplify the
mapping. In other words, decide
whether you need to map all
U.S. Department of the Interior
U.S. Geological Survey —3—Exploring Maps — Information
Latitude Longitude Magnitude
Earthquake data for 1990
21.77S 13.13W 4.7
Area from latitude 45EN to 45ES, longitude 0EE 32.14S 14.10W 4.4
to 45EW. 30.73N 41.66W 4.6
27.13N 44.46W 4.7
33.65N 38.57W 4.8
Note: Magnitudes are measured on the Richter scale,
in which every 1 point difference in magnitude 6.44N 33.08W 5.1
represents a ten-fold difference in energy released by 33.74N 33.29W 4.8
an earthquake. 13.50N 44.79W 4.3
From U.S. Geological Survey, National Earthquake 7.37N 35.29W 5.7
Information Center’s global hypocenter data base. 17.20S 14.28W 4.6
0.54S 19.76W 4.6
14.64N 23.52W 4.2
8.47N 37.50W 4.7
3.62N 31.55W 4.7
1.21S 24.42W 5.1
38.37S 16.59W 5.0
26.71N 44.61W 4.5
0.94N 26.53W 4.9
23.63S 13.41W 4.6
28.45N 43.74W 5.3
44.75S 15.60W 4.8
4.52S 12.29W 5.1
0.07S 17.52W 5.8
44.62N 28.38W 4.8
4.37S 10.78W 4.8
0.54S 14.27W 4.8
39.91N 29.68W 4.3
37.10N 33.04W 4.4
7.14N 34.20W 4.8
0.96N 28.81W 5.2
35.43N 35.65W 6.0
17.70S 13.25W 5.1
9.53N 40.60W 4.9
13.97S 14.51W 5.0
41.31N 29.35W 4.5
27.72N 44.08W 4.9
0.26S 20.89W 4.8
24.89S 13.58W 4.6
43.65S 16.16W 5.3
0.06S 16.67W 5.0
7.62N 36.03W 5.0
35.21S 17.13W 4.9
8.28N 38.51W 4.0
43.73N 28.86W 5.7
2.16N 30.74W 4.7
0.98N 26.70W 4.5
42.55S 16.14W 5.4
Fig. 1 21.03S 11.48W 4.9
1.13S 24.44W 4.9
Fig. 2
U.S. Department of the Interior
U.S. Geological Survey —4—Exploring Maps — Information
Activity II: • Graph paper issues in class to clarify the
Maps With a “Spin” point of view of each group.
• Colored pencils or markers Evaluate maps in newspapers.
In teams of three or four students, Do they have “spin?” Break
research and map the effects of a • Stapler the class into the working
proposed airport three miles groups.
outside of town. Each team is to Procedures:
prepare a presentation based on a 4. Evaluate data and sketch a
set of maps it makes. Teams will 1. As a class, collect basic few test maps. Select only the
represent different points of view: geographic data from various data that support your point of
town government, homeowner’s sources: government, local view or need for information.
associations, business interests, libraries, student observations, Remember the importance of
developers, and State or county businesses, and other good choice of color,
government. Teams will organizations. For example, attractive lettering, and other
emphasize different information. zoning and development aspects of map design in
All teams must use the same data, regulations, weather records, presenting information.
but each team can decide how to locations of landfills and other
generalize the data and map the waste sites, data on land use 5. Prepare the final copies of
patterns they want to present. (residential, farming, materials for a town meeting.
commercial, governmental, Make final copies of maps; be
Time: recreational), boundaries of sure each map has a legend
school districts, locations of and cites sources of
Three evenings of homework for fire departments and fire information. Be able to defend
steps 1-3. hydrants, water supplies, your choice of map type,
pipelines and powerlines, symbols, colors, and
Two 50-minute classes for steps 4 natural hazards (flood plains, generalization or groupings of
and 5. landslides, earthquake risk data. Write notes or a
zones), special scenic or paragraph to briefly explain
One 50-minute class for step 6. historic sites, transportation what each map shows; these
features, wildlife refuges, and will be your speaking notes
Materials needed for each so on. for the town meeting.
group:
2. Sort the data by type: 6. Have a class “town meeting”
• Base map of your locality economic, climatic, where the maps are presented
(several copies) demographic, and so on. and the issues are discussed.
Select data sets that are Allow each group 4 minutes
• Geographic data from which especially important for to present its views, after
to select map topics consideration in planning an which each group has 1
airport. minute for rebuttal. The
• Local newspapers teacher or a student may act as
3. Research local newspapers to moderator, keeping the
• Calculators identify interest groups active meeting on time and on track.
in local issues; briefly discuss
U.S. Department of the Interior
U.S. Geological Survey —5—Exploring Maps — Information
Glossary: Additional activities: Recommended reading:
base map Evaluate news coverage of a local Monmonier, Mark. How to Lie
development issue that uses maps. with Maps. Chicago:
compilation What kinds of maps are being University of Chicago Press,
used? Do the maps appear biased? 1991.
context How? Do different news
organizations present different Wood, Denis. The Power of
distortion opinions, biases, or maps with Maps. London: The Guilford
different information? What seem Press, 1992.
generalization to be the most effective ways to
affect public opinion with maps?
groupings
Invite a geologist to class to talk
isoline about plate tectonics, perhaps
looking at California earthquakes
map design or the geologic story of the
Hawaiian Islands, the Himalayas,
orientation or a nearby National Park.
qualitative Select two quotations, from the
poster information, that seem
quantitative especially pertinent to this activity
sheet, and write an essay that
scale discusses the ideas of both
writers.
bar scale
representative fraction scale
verbal scale
large scale
small scale
spatial data
thematic map
U.S. Department of the Interior
U.S. Geological Survey —6—You can also read
