Exploring Maps — Navigation How do we know where we re The globe is the best way to show in all directions from all points on going the relati

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Exploring Maps — Navigation How do we know where we re The globe is the best way to show in all directions from all points on going the relati Powered By Docstoc
					Exploring Maps — Navigation

How do we know where we're             The globe is the best way to show          in all directions from all points on
going?                                 the relative positions of places, but a    the map. This was an important
                                       globe that can fit in a ship's cabin       breakthrough in mapping. Using a
                                       cannot show the detail needed for          Mercator projection, navigators
Travel depends on the ancient skill
                                       navigation. Flat maps distort the          could draw a straight line to a
of navigation—the ability to find a
                                       placement of features, but can show        destination, sail in that direction, and
way from one place to another and
                                       great detail and are portable.             expect to reach it, allowing for the
back. Columbus was not sure how
                                                                                  effects of ocean currents and other
far he had to go. In his journal he
                                       The transformation of map                  factors.
recorded his latitude observations
                                       information from a sphere to a flat
and estimates of distance traveled
                                       sheet can be accomplished in many          Mercator made longitude lines
underreporting this distance to the
                                       ways, called projections. Map-             parallel and increased the distance
crew, "lest the trip be long."
                                       makers have invented projections           between latitude lines away from the
                                       that show distances, directions,           equator. As a result, extreme
Polar explorers depended on
                                       shapes, or areas as they are on a          northern and southern areas appear
navigational data for survival, as
                                       globe, at least partially. Different       enlarged. For example, Greenland
well as success. Sir Ernest Henry
                                       projections have different                 looks larger than South America,
Shackleton, who attempted to reach
                                       advantages and disadvantages.              although South America is eight
the geographic South Pole several
                                                                                  times as large in reality. This
times between 1902 and 1922, was
                                       Orthographic projections, for              distortion at high latitudes (north and
once marooned on a moving ice shelf
                                       example, show shapes as they appear        south) also makes the distances
and his ship was crushed;
                                       when the globe is viewed from              appear larger than they are. Even
Shackleton's survival depended on
                                       space. Equal-area projections do not       with these disadvantages, this
the latitude and longitude
                                       distort the size of areas but do distort   projection remains one of the most
observations that described the
                                       their shapes. Conformal projections        commonly used.
motion of the ice.
                                       are those on which the scale is the
                                       same in any direction at any point on
Travelers on land need somewhat
                                       the map.
different information from those at
sea. Travelers on solid ground can
                                       Many projections retain one
follow circuitous routes between
                                       geometric quality, and a few retain
important landmarks using schematic
                                       more than one quality, but no single
maps (for example, the A.D. 250
                                       projection can accurately portray
Peutinger map). Seagoing voyagers
                                       area, shape, scale, and direction. (A
need more from their maps, as the
                                       map projections poster available
ocean moves beneath them and the
                                       from the USGS Earth Science
wind and waves push the ship across
                                       Information Center illustrates the
a featureless surface (for example,
                                       features of the most common map
the A.D. 1502 Cantino Planisphere, a
portolan chart). Sailors on the open
sea have kept track of absolute
                                       The Mercator projection was
position using the only reference
                                       designed by Flemish cartographer
points they have: the Sun and stars.
                                       Gerardus Mercator in 1569 to show
                                       compass directions as straight lines

U.S. Department of the Interior
U.S. Geological Survey                                                                                               —1—
Exploring Maps — Navigation

Activity I: Make a                             2. The joint between the two pieces       5. Using the
Mercator Projection                            of paper will be the "equator." Lay       protractor, draw the
                                               the protractor on the paper with the      westernmost line of
                                               flat side on the left. Place the zero     longitude
Follow the directions below to make
                                               point and the 90-degree mark on the       perpendicular to the
a close approximation of the normal
                                               equator (see illustration B). Use the     equator and tangent to
Mercator projection. A few activities
                                               compass to draw a semicircle with a       the original semicircle Illustration E
with the map are included to
                                                                                         at point J (see
demonstrate the important
                                                                                         illustration E).
characteristics of this projection.
                                                                                         6. Set the spacing of the lines of
                                                                                         latitude as
                                                                                         follows: With the
One 50-minute period for steps 1-10.
                                                                                         left end of your
                                             Illustration B        Illustration C        ruler on point T,
After photocopying in step 11, one
                                                                                         align the right
50-minute period for steps 11-14.
                                               6-inch diameter, flat side on the left.   side to point I on
                                               Mark the center (the zero point, Z)       the semicircle; mark
Materials per person:
                                               on the diameter. IMPORTANT                where this line
                                               NOTE: Make all marks lightly in           (TI) intersects the Illustration F
•    Protractor
                                               pencil, unless otherwise instructed.      westernmost
•    Compass                                                                             longitude line. Beginning again at
                                               3. Using a protractor, mark every 10      point T, mark points on the
•    Ruler
                                               degrees around the semicircle (see        westernmost longitude for lines
•    Two sheets of 11 x 17 inch paper          illustration C). Starting at the top,     through points H, G, F, E, D, and C
                                               label these points A, B, C, ..., S.       (see illustration F). Each point
•    Transparent tape
                                                                                         marks 10 degrees of latitude.
•    Sharp pencil                              4. Beginning at Z,
•    Fine point pen, preferably black          measure left along                        7. Draw latitude lines parallel to the
                                               the equator 2/5 of                        equator through these new points. To
                                               a radius (in this                         make the latitudes parallel, measure
                                               case, 1.2, inches)                        the distances between marks on the
                                               and mark a new                            westernmost longitude line; copy
                                               point, T, as shown                        these measurements and mark
1. Tape the two                                                   Illustration D
                                               in illustration D.                        equivalent points on the easternmost
pages together
                                                                                         longitude line. Connect pairs of
along the 17-inch
                                                                                         points (a western and an eastern),
sides and orient the
                                                                                         preferably beginning closest to the
paper as shown in
illustration A, with
the tape on the
reverse side.                                                                            8. Repeat steps 6 and 7 for latitudes
                            Illustration A                                               south of the equator. Notice that on
                                                                                         this projection, lines of latitude are
                                                                                         parallel and spacing between them

U.S. Department of the Interior
U.S. Geological Survey                                                                                                      —2—
Exploring Maps — Navigation

increases away from the equator.         12. Label the latitude and longitude     14. Sketch the outlines of the
Latitudes 90°N and 90°S cannot be        lines along the right and bottom of      continents as shown on other maps
shown on a Mercator projection,          the map. The equator is 0 degrees        available in the classroom. Plot the
because they arc infinitely far from     latitude, and latitude values increase   course between Columbus' home
the equator (although this               in increments of ten to the north and    port and destination; your home
approximate construction does not        south. The westernmost longitude         town and the western coast of
show this).                              line is 180 degrees W; longitude         Africa; and the route of an oil tanker
                                         values decrease in increments of ten     from Kuwait to Tokyo, Japan. Notice
9. Set longitude lines as follows:       to 0 degrees at the Prime Meridian,      that you cannot plot polar
Measure east 0.5 inches from the         and increase again to 180 degrees at     explorations.
westernmost longitude and make a         the eastern edge of the map (see
                     mark on the         illustration H). This map                Extension:
                     equator. This       approximates the characteristics of
                     represents 10       the Mercator projection within about     Obtain a variety of world maps from
                     degrees of          2 percent.                               the school library and compare the
                     longitude. Repeat                                            properties of the projections.
                     this step 17 more   13. Make a bar scale in the margin       Various atlases may prefer different
                     times, and you      below the map. A bar scale is            projections. Which seem to be the
                     will have 180       commonly centered below the map,         most popular projections for world
 Illustration G
                     degrees of          in this case, below the Prime            maps? For detailed maps?
longitude. From each point on the        Meridian (see illustration I). To
equator, use the protractor to draw a    determine the scale at the equator,
perpendicular line. On the Mercator      divide the Earth's equatorial
projection, longitude lines are          circumference (24,902 miles; 40,075
parallel and equally spaced, as          kilometers) by 360 degrees;
shown in illustration G.                 therefore, each degree of longitude
                                         and latitude at the equator equals
10. At this point, the map covers        about 69 mi (about 111 km). Ten
only half the planet (a hemisphere).     degrees of longitude at the equator
Carefully trace this grid in ink.        (about 690 miles) is represented by
                                         0.5 inch on the map; one inch
11. To map the entire Earth, make        represents 1,380 miles. Draw a line
two copies of the original and join      representing 3,000 miles (about
the copies along the one's               5,000 kilometers).
easternmost line of longitude and the
other's westernmost (see illustration
H). Lines should connect
across the
copies. These
two lines both
represent the
Prime            Illustration H          Illustration I
Meridian, the
line of 0 degrees longitude.

U.S. Department of the Interior
U.S. Geological Survey                                                                                             —3—
Exploring Maps — Navigation

Activity II: In the Wake                 Mark these sites on a map of the
of Lewis and Clark                       western United States. Mark State
                                         boundaries and the western
In groups of three or four study the     boundary of the United States as
route of Meriwether Lewis and            they were before the Louisiana
William Clark's travels and the          Purchase.
important events in their journey.
                                         2. Referring to Lewis and Clark's
Time:                                    report, summarize their weekly
                                         progress, marking the map as well as
One week (homework) to scan the          possible. Use symbols for special
journals of Lewis and Clark.             places: important natural landmarks,
                                         the place where they met
One 50-minute class period per step.     Sacagawea, major camp sites, major
                                         obstacles, sites where friendly
Materials per student:                   natives provided important help,
                                         places where they suffered
•    Copies of journals of Lewis and     especially bad weather, places
     Clark (see bibliography)            where they changed from river to
                                         overland travel, etc. Indicate the
•    Notebooks and pencils               boundaries of native cultures along
                                         their route.

Materials per group:                     3. Plan an imaginary trip along part
                                         of the route of Lewis and Clark.
•    Highway maps of the western         How far can you travel in a week?
     United States.                      What obstacles will you face?
                                         Where will you replenish your
•    Information about Lewis and         supplies? What will you take? How
     Clark's expedition (see sources     many are in your party, and what are
     listed below)                       each one's responsibilities? How
                                         much will this cost? How will you
•    Colored markers                     pay for the trip? What can you
                                         accomplish on this trip?
•    Map showing State and national
     boundaries in 1804 and the          Extensions:
     Louisiana Purchase
                                         Keep a journal as if you were with
Procedures:                              the Lewis and Clark expedition for
                                         one week. Include feelings,
1. List places visited by Lewis and      experiences, discoveries, people
Clark and categorize them as natural     met, etc. You may refer to events
landmarks, native villages, sites of     described for the time period
special events, pioneer outposts, etc.   selected.

U.S. Department of the Interior
U.S. Geological Survey                                                          —4—
Exploring Maps — Navigation

Sources of further                     Additional activities:                   Recommended Reading:
information about Lewis
                                       1. Read a diary of another explorer      Biddle, Nicholas, ed. The Journals of
and Clark:                             or pioneer and write a two-page             the Expedition under the
                                       essay comparing this journey with           Command of Capts. Lewis and
Lewis and Clark Trail Heritage                                                     Clark. New York: The Heritage
                                       that of Lewis and Clark.
Foundation, Inc.                                                                   Press, 2 vols., 1962.
P.O. Box 3434,
                                       2. Have a travel agent visit the class
Great Falls, MT 59403                                                           Map of the Conterminous United
                                       and discuss planning for a trip to a                                                             States Showing Routes of the
                                       different continent, and how the
                                       travel business has changed in the          Principal Explorers from 1501
Lewis and Clark National Historic                                                  to 1844.... U.S. Geological
                                       past 40 years.
Trail,                                                                             Survey United States map.
National Park Service                                                              1983.
                                       3. From the reverse of the poster,
1709 Jackson St.
                                       select two quotations that seem
Omaha, NE 68102                                                                 Map Projections. U.S. Geological
                                       especially pertinent to this activity
402-221-3471, 8 am - 4:30 pm Monday                                                Survey poster. 1992.
                                       sheet, and write an essay that
- Friday
                                       discusses the ideas of both writers.
                                                                                Maps of an Emerging Nation—The
                                                                                   United States of America, 1775-
Lewis' and Clark's journals, their
                                                                                   1987. U.S. Geological Survey
report, and secondary descriptive
                                                                                   National Atlas Map. 1987.
writings, which your local librarian
can help you locate.
                                                                                Snyder, J.P. An Album of Map
                                                                                   Projections. U.S. Geological
                                                                                   Survey Professional Paper 1453,

U.S. Department of the Interior
U.S. Geological Survey                                                                                          —5—

Description: Detailed Maps of the Louisiana Purchase document sample