Chapter 3 Models of the Earth

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Chapter 3Models of the Earth
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3-1 Modeling the Planet

• A.  Maps
• a.   Map-A flat, two-dimensional representation
  of Earths surface.
• b. Cartographers-A mapmaker who has devised
  tools to help a map user relate two-dimensional
  images on a map with the three-dimensional world.

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3-1 Modeling the Planet

• B.  Map Projections
• a.   Projections-To reduce distortion,
  cartographers draw world maps in three different
  ways.
• b.  Mercator-Depicts the earth as if it had been
  projected onto a large cylinder and then
  unwrapped. Areas at the poles are distorted in
  this projection.

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3-1 Modeling the Planet

• B.  Map Projections
• c.   Gnomonic Projection- This projection is
  made as if a sheet of paper had been laid out on
  a given point on the earths surface. This
  projection distorts landmass shapes.
• d. Polyconic Projection- In this projection it
  is as if a cone of paper has been wrapped around
  the earth. Lines of latitude and longitude are
  curved slightly. Most landforms have their true
  shape.

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3-1 Modeling the Planet

• C.  Latitude and Longitude
• a.   A grid of imaginary lines placed on the
  earth.
• b.  The earth is divided into Hemispheres. The
  Equator is the imaginary line dividing the north
  from the south. The Prime Meridian divides east
  and west.

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3-1 Modeling the Planet

• c.   The equator is a latitude line that circles
  the world from east to west. Latitude is
  measured in degrees north and south.
• d. The prime meridian is a longitude line that
  runs from north to south. It is measured in
  degrees east and west.

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3-1 Modeling the Planet

• D.  Map Scales
• a.   The scale on a map tells you how the maps
  features compare in size with the earths
  surface.
• b.  This is depicted using a ratio. Ex. one
  inch equals one mile.
• E.  Map Orientation
• a. Always locate north. On new maps it is
  always on top. East is on the right, west on the
  left and south on the bottom.

Compass Rose
N
E
W
S
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3-2 Mapmaking and Technology

• A.  How Cartographers Traditionally Worked
• a.   The USGS created its first map in 1879.
  Its main purpose was to survey and map the West.
• b. Plane Table Surveying was the technique
  originally used. This technique involved
  carrying a plane table to the highest vantage
  point and drawing a map of whatever features they
  could see.

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3-2 Mapmaking and Technology

• B.    How Technology Has Changed in Mapmaking
• a.   The use of airplanes, cameras and radar
  advanced mapmaking tremendously. Why?
•  
• C.    Satellite Technology
• a.   In 1972 NASA launched the first Landsat
  satellite into space.
• b.  False color Image-made up of colors that
  represent images collected by the satellite.
• c. Provide a larger view of the
  earths features

Because you could see the land from above
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3-2 Mapmaking and Technology

• D.    Computer Technology
• a.   Computers are needed to process the images
  collected by satellites. Advances in computer
  technology have made it easier and faster to
  process this information.

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3-2 Mapmaking and Technology

• b.  Global Positioning System (GPS)-Allows people
  to determine their position, speed, and time
  anywhere in the world.
• c.  Triangulates its position using the
  satellites in the sky.
• d. Geographic Information Systems
  (GIS)-Combines satellite images and surveys. See
  page 52.

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3-3 Topographic Maps

• A.   Qualities of Topographic Maps
• a.   Depicts the features of an area using
  contour lines and symbols.
• b.  7.5 maps-represent 7.5 minutes of latitude
  by 7.5 minutes of longitude.
• c. Why are these maps important?

They show us the location and elevation of
landmarks

• http//erg.usgs.gov/isb/pubs/booklets/symbols/

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3-3 Topographic Maps

• A. Qualities of Topographic Maps
• d.   Contour Lines- Narrow brown lines on
  topographic maps that indicate the landscapes
  elevation. They connect points of the same
  elevation.

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3-3 Topographic Maps
The contour interval can be calculated by taking
the difference in the two bold lines and dividing
by 5. Ex. (800ft-700ft)/520 ft

• e.  Contour Interval- The difference in elevation
  between two consecutive contour lines.
• f. Contour lines that are close together
  indicate steep terrain lines that are far apart
  indicate a gentle slope.

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3-3 Topographic Maps

• B.   Understanding Topographic Map Symbols
• a.   These symbols help to understand what
  features are on the map. See page 697.
• b. Magnetic Declination- Angle by which a
  compass needle will vary from true north.

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3-3 Topographic Maps

• C.   Using Topographic Maps
• a.   Shape of the land can be determined by
  making a profile from a topographic map. See
  page 57.
• b. A map scale indicates how much land is being
  covered in a given area on the map.