Models of the Earth: Using and Interpreting Maps

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Models of the EarthUsing and Interpreting Maps

• Finding Locations on Earth
• Mapping the Earths Surface
• Topographic Maps

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Thought Question

• What is the purpose of maps?
• How are positions on planet Earth
  represented/located?
• Explain how you would go about creating a map by
  hand. What kinds of tools would you need? What
  variables would you need to consider?

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Objectives

• Distinguish between latitude and longitude
• Explain how latitude and longitude can be used to
  find a location on Earth
• Explain how a magnetic compass can be used to
  find directions on Earth
• Describe the characteristics and uses of three
  types of map projections
• Define scale and explain how it can be used to
  find distance on maps
• Explain how elevation and topography can be shown
  on a map
• Interpret a topographic map

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Why Maps?

• For thousands of years, people have used maps
• to define borders and to find places.
• Cartography is the science of mapmaking.
• Cartographers use an imaginary grid of parallel
  lines and vertical lines to locate points on
  Earth.
• The equator circles Earth halfway between the
  north and south poles separating Earth into two
  equal halves called the northern hemisphere and
  the southern hemisphere.

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Latitude

• Parallels- imaginary circles running east/west on
  the globe determine how far north/south one is
  named because they parallel the equator
• Latitude- the angular distance from north and
  south of the Equator measured in degrees (90
  intervals)
• Latitudinal Great Circle- Equator is the only
  latitudinal great circle (any line that separates
  the earth into two equal parts)

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Latitude

• Latitude is thus measured from 0 at the equator
  to 90 at the poles.

• Locations north of the equator are referred to by
  degrees north latitude (N).
• Locations south of the equator are referred to by
  degrees south latitude (S).

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Longitude

• Meridians- lines running north/south on the
  globe, pole to pole determine how far east/west
  one is
• Prime Meridian- the point 0 longitude runs
  through Greenwich, England
• Longitude- the angular distance east or west of
  the Prime Meridian all measured from 0- 180
  east or west of the Prime Meridian
• Longitudinal Great Circles- any two meridians
  running directly opposite (180) from one
  another bisect the globe

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Longitude

• Points west of the prime meridian are numbered
  from 0 to 180 west longitude (W).
• Points east of the prime meridian are numbered
  from 0 to 180 east longitude (E).

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Locating Places with Coordinates

• Both latitude and longitude are needed to
  precisely locate positions on Earth.
• For example, the location of New Orleans is
  2957N, 9004W.
• Note that latitude comes first in reference to
  the coordinates of a particular location.

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Assessment

• Match the following terms with their definitions.
• ___ latitude
• ___ longitude
• ___ prime meridian
• ___ equator

D B A C
A. the reference point for longitude B. the
distance in degrees east or west of 0 C. the
reference point for latitude D. the distance in
degrees north or south of 0
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Assessment

• Identify whether the following statements are
  true or false.

false true false true
_______ A degree of longitude always represents
the same distance. _______ If you travel west
across the International Date Line, you advance
your calendar one day. _______ Lines of latitude
are not perfectly parallel to each
other. _______ When referencing a specific place
on Earth by its coordinates, latitude always
comes first.
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Direction Finding

• Geomagnetic Poles- the point above the earths
  poles where all magnetic lines converge
• The earth behaves as a giant magnet with areas
  near the north and south pole acting as the ends
  of the magnet this affects compasses different
  amounts in different areas
• Magnetic Declination- the angle between the
  direction of the earths geographic pole and the
  direction in which a compass needle points
• True North- direction of the geographic north
  pole

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Thought Question

• Describe one type of map that you have seen or
  used. What symbols are used? How are land forms
  depicted? Name the type of map if you know it.
• What fields of science use maps and what are the
  maps used for?
• Compare and contrast magnetic north and true
  north.

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Mapping The Earths Surface

• Maps are flat models of a three-dimensional
  object, Earth.
• All flat maps distort to some degree either the
  shapes or the areas of landmasses.
• Cartographers use projections to make maps.
• A map projection is made by transferring points
  and lines on a globes surface onto a sheet of
  paper.
• Map Projection- any flat map that is a
  representation of a three dimensional object
  three types Mercator, Gnomonic, and Conic

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Mercator Projection

• Mercator- a map projection in which both the
  meridians (evenly spaced) and parallels (unevenly
  spaced) are straight and parallel, forming a grid

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Gnomonic Projection
Gnomonic- parallels appear unevenly spaced,
concentric circles meridians appear as straight
lines radiating from a central point all great
circles appear as straight lines
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Conic Projections

• Conic- meridians converge at the poles the
  parallels appear as equally spaced, concentric
  curves
• Polyconic Projection- several conic projections
  put together to form a larger map

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Map Reading

• Legend- the portion of a map that lists all
  symbols and their meanings, distances, and
  intervals aides map reading
• Map Direction- maps are usually drawn with north
  at the top of the page and south at the bottom
• Scale- the comparison of the distance on the map
  to the actual distance covered
• A graphic scale consists of a line that
  represents a certain distance, such as 5 km or 5
  miles.
• A fractional scale expresses distance as a ratio,
  such as 163 500.

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Topographic Maps

• Topographic Map- scientific maps that show
  surface features (such as mountains and valleys)
  by using contour intervals changes 3D into 2D
• Topographic maps use lines, symbols, and colors
  to represent changes in elevation and features on
  Earths surface.
• Topography- surface features of the earth
• Elevation- the height, in feet or meters, above
  or below sea level
• Mean Sea Level- the point located between the
  highest and lowest tide levels of the ocean

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Topographic Maps
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Making Topo Maps

• Contour Lines-lines on a map that connect points
  of the same elevation
• Contour Interval- the difference (in feet or
  meters) from one contour line to the next
• Relief- the change in elevation from the lowest
  to the highest points of an area sometimes
  referred to as vertical relief
• Index Contours- every fifth contour line on a
  topo map generally bold

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3D to 2D
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Depression Contours

• Depression contour lines are used to represent
  features that are lower than the surrounding
  area.
• On a map, depression contour lines have
  hachures, or short lines at right angles to the
  contour line that point toward the lower
  elevation, to indicate depressions.

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Section Assessment

• Match the following terms with their
  definitions.
• ___ projection
• ___ contour interval
• ___ map legend
• ___ map scale

A. the difference in elevation between two
side-by-side contour lines B. a diagram that
explains what the symbols on a map
represent C. a map made by transferring points
and lines on a globes surface onto a sheet of
paper D. the ratio between distances on a map and
actual distances on the surface of Earth
C A D B
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Section Assessment

• What does it mean if a map says Scale 1100
  000?

This fractional scale means that one unit on the
map represents 100 000 units on Earths surface.
For example, one inch on the map would equal 100
000 inches on Earths surface.